Amiga Plus 1995 #2/Amiga Plus CD - 1995 - No. 2.iso/internet/faq/englisch/comp.arch.storage

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Archive-name: arch-storage/part1
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Posting-Frequency: monthly

Rod Van Meter, Joe Stith, and the gang on comp.arch.storage

Information on disk, tape, MO, RAID and SSD can be found in part 1 of
the FAQ.  Part 2 covers file systems, hierarchical storage management,
backup software, robotics, benchmarking, MTBF and miscellaneous
topics.


1.     Editor's Note

2.     Disclaimer

3.     Original Editor's notes

4.     Truly Frequently Asked Questions

5.     Tape
5.1.   Cartridge vs Cassette
5.2.   Longitudinal
5.3.   Serpentine
5.4.   Helical Scan
5.5.   9-track {brief}
5.6.   3480/3490/3490E {brief}
5.6.1. New IBM Tape (NTP)
5.7.   QIC {brief}
5.8.   4mm {brief}
5.9.   8mm {brief}
5.9.1. Mammoth {Brief,New}
5.10.  DEC/DLT {full}
5.10.0.1. DLT4000 (From DEC)
5.10.0.2. DLT2700 (from DEC)
5.10.0.3. DLT2000 (from DEC)
5.11.  Metrum VHS {brief}
5.12.  VCR VHS
5.13.  19MM (D1 and D2) {Brief}
5.14.  ID-1
5.15.  D-2
5.16.  StorageTek Helical {Brief}
5.17.  Optical {brief}
5.18.  D-6 {brief}
5.19.  D-3 {brief}

6.     Disk
6.1.   CAV, ZCAV and CLV
6.2.   Optical {Brief}
6.2.1. CD-ROM
6.2.2. WORM {brief}
6.2.3. Erasable
6.2.3.1. Magneto-Optical Physics
6.2.3.2. Magneto-optical, 5.25-inch
6.2.3.3. Magneto-optical ZCAV, 5.25-inch
6.2.3.4. HP Corsair {Brief, New}
6.2.3.5. Maxoptix T4-1300
6.2.3.6. Asaca HSMO {Brief}
6.2.3.7. Other Multi-beam MO {None}
6.2.3.8. 3.5-inch MO {Brief, New}
6.2.3.9. Nikon 12-inch MO {Brief}
6.2.3.10. Sony 12-inch MO {Brief,New}
6.2.3.11. NEC 12-inch MO {Brief,New}
6.2.3.12. Electron-Trapping {None}
6.2.4. Dual Function {None}
6.2.4.1. IBM {None}
6.3.   Magnetic
6.3.1. 5.25-inch
6.3.1.1. Seagate
6.3.2. 3.5-inch
6.3.2.1. IBM
6.3.3. Bernouli {None}
6.3.4. Floptical {Brief}
6.3.5. Mainframe {Brief}
6.4.   Other
6.4.1. Holographic Storage Products {Brief}

7.     RAID {Full}
7.1.   RAID Levels
7.2.   RAID-6
7.3.   John O'Brien and RAID-7
7.4.   RAID Papers
7.5.   R-Squared {Brief}
7.6.   Sun {Brief}
7.7.   the RAIDbook {Brief,New}
7.8.   Software Striping {Brief}
7.9.   RAID Vendors {New}

8.     Solid State Disk (SSD) Frequently Asked Questions (FAQ)

9.     Other Devices
9.1.   SyQuest Removable Cartridge hard Drives
9.2.   Kalok removable cartridge hard drives

10.    RAIT (Redundant Arrays of Inexpensive Tape)

11.    RAOT (Redundant Arrays of Other Things :-)


        Many items merely identified, not described.

        Last updated: 95/2/12

        Most recent changes:
        Tape Arrays
        ***long list of RAID vendors***
        IBM 10.8 GB 3.5" HD
        (part 2)
        list of backup vendors
        ADSM & ARCserve
        ***improved HSM -- includes long list of vendors***
        Maxoptix & Qualstar autochangers
        contacts for mass storage conferences

        comp.arch.storage:
                Storage system issues, both software and hardware


------------------------------
Subject: [1] Editor's Note
From: Editor's Note

I took over the maintenance of the C.A.S FAQ from its originator, Joe
Stith ([e-mail], Fermi National Accelerator Laboratory, at the
time), in July '94. I have begun additions and edits of my own. It
should be available on the various FAQ servers. Apologies for the
under-construction formatting and lack of better referencing.

I will add as my expertise and time allows and will include
submissions sent to me (Rod Van Meter, [e-mail]) and
information put into the newsgroup by others.  Yes, some of the
submittals are from vendors (including me, see the disclaimer).  If
you post to the newsgroup and find yourself quoted in this FAQ but
wish to be removed, please let me know.

There is more information in my (still primitive) WWW version of the
FAQ, including more commercial info. It is temporarily available at
http://alumni.caltech.edu/~rdv/comp-arch-storage/FAQ-1.html, but this
is probably not a good permanent home for it (volunteers?). I have
also started working on a Japanese translation available there (only
about 10% complete). There is also a good group of FAQs (including
this one) stored at http://www.cis.ohio-state.edu/hypertext/faq/;
prettier and easier to use but with only the info I actually post.

The size of these FAQs is getting out of hand; I'm open to suggestions
on material that doesn't really belong in a FAQ or areas where I'm
simply too verbose (I may reduce the DLT info since there is now a
separate FAQ).

SHMO: when you see this, it means "Somebody Help Me Out!" I'm actively
soliciting information on this topic.

See the copyright notice near the end.

------------------------------
Subject: [2] Disclaimer
From: Disclaimer

I work for ASACA, which makes Metrum's robotics and makes a 12
MB/sec. magneto-optical disk drive, and resells AMASS in Japan. This
information is included so you can identify my bias. Obviously the
things that I know the most about are the best-represented. I attempt
to be as impartial as possible; if you have complaints about my
fairness, let me know. None of this should in any way be construed as
the official opinions of ASACA, and may not even represent MY
opinions.

------------------------------
Subject: [3] Original Editor's notes
From: Original Editor's notes

I believe a reference would be useful and I am willing to pull
it together...

I have included the original call for votes and will go through that
list for other ideas to include.

I will also format this for sending to news.answers, misc.answers,
and comp.answers.

As I am writing this, "{None}" indicates I have not written anything
for it yet, {Full} indicates it is OK, while {Brief} indicates somewhere in
the middle.

{New} indicates some new information has been provided.

=========DISCLAIMER=====

        This information is believed to be reasonably accurate although I do
not verify every submission.  No legal liability is assumed.  See full
disclaimer at end.

------------------------------
Subject: [4] Truly Frequently Asked Questions
From: Truly Frequently Asked Questions


Also see the miscellaneous section near the end of part 2 of the FAQ.

* How do I connect X to Y?

Try asking in the appropriate comp.periphs.x or comp.sys.y groups.

* What about the jumper settings for my Yoyodyne 4000?

Try asking in the appropriate comp.periphs.yoyodyne group.  This group
attempts to keep the discussion at a higher level.

* Can somebody recommend a PC or Unix backup package? (SHMO)

The Aug. '94 issue of PC World has an article covering PC tape
drives (mostly QIC), and covers backup software to some extent as
well. Try asking this question in the PC-related newsgroups.

I've started adding a list of backup software to part 2 of this FAQ,
though it's not very complete yet.

* What about DAT/DLT/8mm/...?

Covered in the sections on tape drives & media. There is also a
DLT-specific FAQ maintained by a guy from DEC posted occassionally
here.

* Does anybody have the phone number of...? (SHMO)

Anybody keeping a list of the phone numbers people ask about
frequently? I don't have one.

For the WWW-enabled, check out
http://www-atp.llnl.gov/atp/comp-comm.html.

* What about RAID7?

See the description under RAID arrays; NOT a popular topic around
here.

* MTBF?

This topic is responsible for generating the most heat in this group.
There are a few sentences about it in part 2 of the FAQ, but I'm not
qualified to write this section (and/or not willing to suffer the
public humiliation :-).

------------------------------
Subject: [5] Tape
From: Tape
(No compression added in calculations unless specified otherwise)

------------------------------
Subject: [5.1] Cartridge vs Cassette
From: Tape
Cartridge has only one reel (i.e.  3480, DLT).  Cassettes have two
reels (i.e., 8mm, 4mm, 19mm, VHS) and may not need to be rewound to
dismount.

------------------------------
Subject: [5.2] Longitudinal
From: Tape
have heads that write bit streams that are parallel to the edge of
the tape.

------------------------------
Subject: [5.3] Serpentine
From: Tape
are longitudinal that write the full length of the tape, then turn
around and write the length of the tape in the opposite direction with the
heads in a slightly different position.  This process may repeat many times.

------------------------------
Subject: [5.4] Helical Scan
From: Tape
are like your VCR with a rotating head mounted at an angle writing
"swipes" at an angle not parallel to the edge of the tape.  The tape is moved
only slightly between swipes.  Two or so longitudinal tracks may also be used
for fast positioning purposes.

------------------------------
Subject: [5.5] 9-track {brief}
From: Tape
The old 2400 foot round reel of tape written at 800, 1600, or 6250 BPI.

------------------------------
Subject: [5.6] 3480/3490/3490E {brief}
From: Tape

        Square cartridge:
        serpentine
                IBM 3480 - 18 track - 200 MB/cartridge, 1984
                IBM 3490 - Smaller packaging, IDRC standard, 1989
                        reports that it is a 3480 in ID string
                IBM 3490E - 36 track, double length - 800 MB/cartridge
        native, 1992
            IDRC data compression is also available.

These drives have traditionally come from the mainframe vendors --
IBM, Fujitsu, Storage Tek, etc. They were originally very large
objects, with vacuum columns and mainframe interfaces, the size of
large filing cabinets.

However, recently they have become available in smaller packages, 19"
rack mount or table top, and with interfaces such as SCSI.

Here's one from last year that I recently dug out of some old mail:

IBM has just made generally available the following:
  3490E Model E SCSI tape drive
  fast/wide differential
  IDRC compression
  3 MB/sec at the tape head, 6.5 MB/sec with compression
  approx 800 MB tape capacity with out compression, 2.4 GB with a 3:1 comp
  7 tape CSL(cartridge stack loader)
  Desk top and rack mount
  List $27,000

[e-mail], 94/4/11

There's also a standalone drive with a small autoloader from a company
called Overland Data. Their L490e is a win because it reads and writes
both 18 and 36 track tapes. At $20K it's reasonably priced. For the
www-enabled, see http://www.ovrland.com/~odisales.
([e-mail], 94/12/21)

------------------------------
Subject: [5.6.1] New IBM Tape (NTP)
From: Tape

Unannounced product from IBM that has been demonstrated at mass
storage conferences. Same form factor as 3480, serpentine. 9 MB/sec.,
10GB/cart. Bare drive should retail ~$35K, 1Q95. Two SCSI interfaces?
Robotics also planned. ([e-mail], 09/30/94)

------------------------------
Subject: [5.7] QIC {brief}
From: Tape
        Quarter Inch Cartridge.  Primarily low-end (ie, PC) available from
multiple vendors but 3M is pushing it into midrange market with estimates of
100 Gigabytes per cartridge by 1999. Two-reel cassette.

In Dec '94, 3M, Sony, HP and others announced a new format, 2.3 times
the capacity, available mid-1995. The cartridge and drive mechanics
apparently change. It will be .315 inch tape instead of .25, with 750
feet of media in a cartridge. (rdv, 94/12/16)

------------------------------
Subject: [5.8] 4mm {brief}
From: Tape
        Multiple vendors.
        Initially for home audio market.
        Original product held 1.3 GB on one 60 meter tape at about 180
KB/second.  Search speeds run about 200 times nominal speed.
        DDS (Digital Data Storage) format has overtaken the DATA/DAT format.
    Two-reel cassette.

------------------------------
Subject: [5.9] 8mm {brief}
From: Tape

Sony developed transport designed initially for home video market.
Exabyte has U.S. rights with Kubota qualifying as a second source when
needed.

EXB 8200 model holds 2.3 Gigabytes per tape at 220 KB/sec

EXB 8500 model holds 5 Gigabytes per tape at 500 KB/sec

Search speeds of the 8200 is dismal, but is significantly improved in
later models.  Compression and half-height (standard is full-height
5.25-inch) features are also available.

------------------------------
Subject: [5.9.1] Mammoth {Brief,New}
From: Tape

Mammoth is the new Exabyte drive. It reportedly holds 20 GB
uncompressed per cartridge, with a transfer rate of 3 MB/s. Exabyte
has been touting this drive since at least April '93. It is finally
due out "soon". (rdv,95/1/13)

------------------------------
Subject: [5.10] DEC/DLT {full}
From: Tape

Digital Linear Tape (DLT)
TZ87 (DLT2000) - 10 GB native per cartridge
See also robotics (DLT2700 is 7 tape library)
Ref: Digital's Customer Update, March 14, 1994
Serpentine recording.

Developed from DEC's TK50 & TK70 technology. The unit that developed
this was sold to Quantum.

DLT is the new tape technology getting the most air time around here.
There is also a DLT-specific FAQ maintained by a guy from Quantum.

From the newsgroup:

Tape uses a special hook for load/unload mechanism.

DEC is the initial vendor, but other vendors are re-selling them
(sort of like TTI's reselling of the Exabyte 8mm tape drive).

Transfer rate of 2.5 MB/sec, but that assumes 2:1 compression, so it
is 1.25 MB/Sec native.  Likewise the 20 GB cartridge is 10 GB native.

DLT4000 ($2K upgrade from DLT2000) soon (9/94?)  Double the capacity.
Some agreement with Cypher. Still not shipping in quantity, 1/95.

Can be used on NON-DEC systems (standard SCSI interface).

One report of a batch of tapes that were "too wide".

>[e-mail] (Michele Michelotto) wrote:
>You're comparing the top QIC format with the rather new DLT
tecnology.  What is so special about DLT? I'll try to answer:

>1. Serpentine format means that there are several parallel tracks.
the head goes down the first track and comes back down the second one
etc.  If I need to access a file at the end of the "logical tape" and
the drive knows that it is at the beginning of the 52th track it goes
directly to the 52th track and start seeking on it. So the worst case
access time is close to the rewind time (about 100 sec) the average
access time is about (60 sec).

>2. the unit I tested was a 6 GB/cartridge (no compression) 700
kB/sec. the cartridge had 112 tracks but since the drives use two
heads, it could access track N and track N+54 together. So it looked
like a 54 track cartridge. Now it's very easy to put 4 (or 8) heads in
the drive and double (or multiply by 4) the transfer speed while
maintaing the backward compatibility (with 8 head you use only head #1
and #5 to emulate a 2 heads unit).

>3. DEC is selling to the OEM a DLT4000 unit with 20GB uncompressed
(40GB with compression). [may be available 9/94].  [Thinner, longer
tape plus somewhat higher density and slightly more efficient
packing/blocking]

DLT cost $5K US for 20GB drive, $10K for a 140GB stacker, $150K for a
3.2 TB robot.

Autochangers are made by DEC, Odetics (available through EMASS) and
Metrum.

Piping tar into dd, with a bs=64k can increase your speed.

The drives have a tape mark directory that is used for a SPACE
command, but if you just SPACE 1 FILEMARK multiple times, efficiency
is poor (and is the fault of the software implementation as it should
"SPACE n FILEMARKS").

Submitted (approved?) ANSI standard, but that does not mean anyone
other that DEC is doing anything more than OEM'ing it.

------------------------------
Subject: [5.10.0.1] DLT4000 (From DEC)
From: Tape


Streaming tape drive
Quoted 40 GB includes 2:1 compression
Quoted 3.0 MB/sec includes 2:1 compression
Extended 5.25-inch form factor
SCSI-2 interface, either single-ended or differential,
optional fast SCSI.
Compression is DLZ (Digital Lempel-Ziv)
"...a head life of 10,000 hours (compared to 2,000 hours for
other tape products), a recommended average of 10,000 read/writes per
cartridge, and an MTBF of 80,000 hours."
Search speed averages 68 seconds
Repositioning time 1.3 seconds
Hard error rate: 1 x 10**17 bits read
Undetected error rate: 1 x 10**30 bits read
Serial serpentine (128 tracks), variable block
bits/inch: 82,000
Tracks/inch: 256
Recording media: CompacTape (tm) IV
0.5 in x 1,700 ft x .3mi thick
Cartridge: 4.1 x 4.1 x 1 inch
shelf life: 10 years
Height: 3.235 in, width: 5.7 in, length: 9 in
Reliability: 80,000 MTBF
Media reliability: 500,000 passes in start/stop mode (or an
average of 10,000 uses/cartridge)


------------------------------
Subject: [5.10.0.2] DLT2700 (from DEC)
From: Tape

random access, seven tape, 1 drive library
rack mountable 8-inch form factor
includes operator control pannel and LED indicators
400,000 mean mechanical cycles before failure
uses a 7 cartridge magazine.
Magazine "precheck": 75 seconds per magazine
Cartridge load (max): 28 seconds
Cartridge unload (max): 30 seconds
SCSI command set for robotic commands
Subsystem reliability: 30,000 power-on hours
Height: 10.4 in, width: 8.7 in, length: 27 in
weight: 65 lbs


------------------------------
Subject: [5.10.0.3] DLT2000 (from DEC)
From: Tape

CompacTape (tm) III
Capacity: 20 GB/cartridge
        (assumes 2:1 compression)
1.25 MB/sec.


        [e-mail] (Rodney D. Van Meter), [e-mail]
(Peter Van Epp), [e-mail], [e-mail],
[e-mail]


------------------------------
Subject: [5.11] Metrum VHS {brief}
From: Tape

        Metrum, 800/METRUM-2 ([phone])
        Drive: RSP-2150, 2MB/sec sustained, 4MB/Sec burst
        ST-120 cartridge holds 14.5 GB
        ST-160 cartridge holds 18 GB
        See also robotics


------------------------------
Subject: [5.12] VCR VHS
From: Tape

This appeared recently in the newsgroup, but I don't know anything
about it. This is the widget that takes data in one end and spits out
a video signal that you can pipe into your home VCR to use your it for
data storage. It's only $350, but, for those of us in the U.S. and
Japan, it doesn't work for NTSC VCRs.

From: [e-mail]
Subject: VTS Tech Specifications for Users
Date: Mon Nov 28 09:24:29 PST 1994
X-Gateway: [e-mail]

Having received a lot of questions from different users of VTS 1020,
I'd like to answer them giving short specifications of this unit.
1. CAPACITY: 4 GB Compressed / 2 GB Uncompressed on one E-180 cassette.
             The amount of data grows according to the tape length.
2. SPEED:    100 KB/sec for PC/AT 286-16 Mhz
             200 KB/sec for PC/AT 386-33 Mhz etc.
3. SOFTWARE: The current version is for DOS. Windows support-DOS Window.
             Read/Write verification is provided.
4. VIDEO:    PAL/SECAM System, VHS Tape


------------------------------
Subject: [5.13] 19MM (D1 and D2) {Brief}
From: Tape

19mm is 3/4 inch helical scan tape.  Two varieties exist, D1 and D2.
Both originated from broadcast and/or data recorder applications,
where the data/signal was analog in nature.  They have been modified
for digital use, with error correcting capabilities added.

Data rates are in the 8-45 MByte/sec range, with storage capacities
in the 25-175 GB range in physically different size cartridges with
different length tapes, but all fitting into the same tape drive unit.

------------------------------
Subject: [5.14] ID-1
From: Tape

SHMO: I'd like to hear more of people's experiences using these
things.

Note: I would recommend you talk to people who've used these things
before buying one!

DataTape (Pasadena, CA, formerly a division of Kodak), I believe, has
an ID1 system available, with a HiPPI interface.

Sony makes several models of a D-1-based data drive; the format is
generally referred to as ID-1. It comes in different models, with
equivalent price tags, that run from 8 to 32 MB/sec. The original
machine had a VME interface that was extremely low-level ("any lower
and you'd have to turn the spindles by hand," someone said); now there
is a HiPPI interface available from a company called TriPlex. I
understand the HiPPI interface also adds another layer of ECC to
improve the otherwise abyssmal error rate (10^-10 becomes ???). Sony
is also supposed to be doing their own SCSI and HiPPI interfaces. I
don't know the status nor if they are compatible with tapes from the
TriPlex unit (I suspect not).

These are very expensive -- $100K+, but for people with the need,
they've got the speed.

        ([e-mail], (John Stephens),
    [e-mail] (Rod Van Meter))

------------------------------
Subject: [5.15] D-2
From: Tape

Ampex (and Sony??) support D2.  Data rates are in the 15 MByte/sec
range.

The Ampex tape transport and head system were sold through E-Systems
(EMASS), who built the storage controller and sold it as the ER-90 and
coupled it with Odetics robots. Ampex now makes their own interface
for the unit, sold as the DST. They also make their own very fast
robotics.

The ER-90 is popular with the oil crowd. I don't know if the tapes are
interchangeable with the DST.

(rdv, 12/94)

DD-2  (19mm Data D-2 Format)

Ampex DST General:

3 cartridge (cassette) sizes - 25, 75, 165 gigabytes (uncompressed).
15 megabyte/sec. sustained (20 megabyte/sec. burst) transfer rate (per
drive).  Up to 800 megabyte/sec. search speed (per drive).  Smart DD-2
format includes partitioning and system zones to maximize storage
efficiency and speed data access.  3 layers of Reed-Solomon error
correction, with read-after-write verification and automatic rewrite
yield error rate of 1 in 10E15 bits read.  Drive(s) dual ported SCSI-2
(16 bit fast, differential).

DST 310 Tape Drive:

All 3 cartridge (cassette) sizes supported - 25, 75, 165 gigabytes
(uncompressed).  Rack mount or table top configurations.  Single unit
price: $120K.

Ampex Corporation
401 Broadway, M.S. 3-46
Redwood City, CA 94063-3199
Inquiry:  415-367-2982
Facsimile:  415-367-3850
Internet:  [e-mail]

(see also Ampex under autochangers -- they make their own for this
tape drive)

([e-mail], 94/12/23)

------------------------------
Subject: [5.16] StorageTek Helical {Brief}
From: Tape

Storage Tek has been working on a project called Redwood for a number
of years. The cartridge will be 3480 form-factor, to protect users'
investment in Storage Tek robotics. Capacity of 20 GB/cartridge,
transfer rates of 15 MB/sec.(? unconfirmed). Due out ?end of 94?
Probably expensive. ([e-mail] (Rod Van Meter))

The ESCON interface is in betatest; SCSI fast & wide due out soon.
([e-mail], 94/12/19)

------------------------------
Subject: [5.17] Optical {brief}
From: Tape

A company called Creo, from Canada I believe, makes a large tape drive
that uses ?1"? tape and gets a terabyte of data on a $10,000 reel.
The time to read the media (media granularity) is huge; at 3
MB/sec. it takes almost four days to read a tape!

------------------------------
Subject: [5.18] D-6 {brief}
From: Tape

From Toshiba & BTS, originally designed as a full-speed (~150MB/sec.)
digital HDTV VTR. A model with a HiPPI interface is supposed to be
available end of 94. The video version is priced at US$300K+. I
believe the tape transport and cartridge are the same as for D-2,
though the tape material is different.

(4/94, rdv)

------------------------------
Subject: [5.19] D-3 {brief}
From: Tape

From Martin Marrieta, mentioned here on the net recently. Very fast
(10.8 MB/sec.), ~$125K. General availability scheduled for 11/14/94
(9/20/94, [e-mail]). I believe the cartridge is the same as
Betacam, so look for the broadcast autochanger companies here (rdv).

------------------------------
Subject: [6] Disk
From: Disk

------------------------------
Subject: [6.1] CAV, ZCAV and CLV
From: Disk

Many disks (hard, floppy and optical) run in CAV (Constant Angular
Velocity) mode. In this case, the disk spins at a constant rate, and
there are the same number of sectors per track on inner and outer
tracks. This means that the bits are farther apart on the outer
tracks, potentially wasting space. The transfer rate is
constant, as the number of bits/track is same and the time/track
doesn't vary.

CDs (and video laser disks, I believe) and early Macintosh floppies
run at Constant Linear Velocity (CLV). That is, the bits are all
roughly the same size, and the rotations per minute of the drive is
adjust as the head moves in and out. This gives the best areal
density of bits, at the sacrifice of seek speed, since every seek
requires an adjustment of the rotation speed. The transfer rate is
constant, as the size and spacing of bits is constant and the linear
velocity is constant.

The current rage is ZCAV, Zoned Constant Angular Velocity. Most modern
SCSI disks have this feature, and the newest MO drives do, as well.
There are a number of zones defined on the disk. The number of sectors
per track is different in each zone. Thus, the data is packed more
densely than normal CAV, but seek speed is not sacrificed. Another
effect of ZCAV is that the media transfer rate varies depending on the
head position, because the time/track is constant and the bits/track
vary; for example, the Seagate ST12450W Barracuda drive varies from 68
to 113 Mbits/sec, almost a factor of two different.

------------------------------
Subject: [6.2] Optical {Brief}
From: Disk
        See also Robotics section for library options.
        Slower than magnetic disks (in general)

------------------------------
Subject: [6.2.1] CD-ROM
From: Disk
Historically produced off-site at significant first-copy cost but
small cost for high volumes.  Now on-site 'authoring' systems are available.
Standard formats are available. Ads have been posted to the net
offering services for as little as US$60 to convert a tape to CD.

------------------------------
Subject: [6.2.2] WORM {brief}
From: Disk
Write-Once-Read-Many
Standards are less firm between vendors.

------------------------------
Subject: [6.2.3] Erasable
From: Disk
Better standards than WORM

------------------------------
Subject: [6.2.3.1] Magneto-Optical Physics
From: Disk

Magneto-optical disks are plastic or glass disks coated with a
compound (often TbFeCo) that has special properties. The disk is read
by shining a low-intensity laser (originally infrared, but experiments
are being conducted all the way up to blue, I believe; the shorter the
wavelength the higher the possible density, all things being equal
(which they never are)) onto the media and examining the polarization
of the reflected light. To write, a higher-intensity laser is used to
heat the material up to its Curie point, where it becomes susceptible
to a magnetic field. When the media cools again, its state is
"frozen". The polarity of the reflected light during a read depends on
the polarity of the magnetic field under which the media was last
cooled. Once it has cooled it is no longer suceptible to magnetic
fields. Thus, it can be compared in a sense to paleomagnetism.

------------------------------
Subject: [6.2.3.2] Magneto-optical, 5.25-inch
From: Disk
Same number of sectors on each track whether or not track is near
center or outer edge.  640 MB. Made by IBM, HP, Sony, Ricoh, others?

------------------------------
Subject: [6.2.3.3] Magneto-optical ZCAV, 5.25-inch
From: Disk

        Zoned constant angular velocity - more sectors on outer tracks.
        GB: 1
        ECMA standard 183 going through ISO Fast Track.
        ADSTAR demonstrated (6/93), San Jose, CA, 408/256-7895.


------------------------------
Subject: [6.2.3.4] HP Corsair {Brief, New}
From: Disk

1.3 GB on a double-sided cartridge.

See also under MO autochangers in part 2.

------------------------------
Subject: [6.2.3.5] Maxoptix T4-1300
From: Disk

Does 1.3, 1.0 (read only) and 650 MB media. Max sustained read 2.0
MB/sec.

See also under MO autochangers in part 2 for contact info.

(rdv, 95/02/14)

------------------------------
Subject: [6.2.3.6] Asaca HSMO {Brief}
From: Disk

My company (Asaca) makes a 12.24 MB/sec. MO drive that uses custom
media and two four-beam heads in parallel to increase the transfer
speed. Expensive.

Call John Clemens in our L.A. office, [phone]

------------------------------
Subject: [6.2.3.7] Other Multi-beam MO {None}
From: Disk

------------------------------
Subject: [6.2.3.8] 3.5-inch MO {Brief, New}
From: Disk

Generally looks like a slightly overweight floppy. All current ones
are single-sided.

First generation 3.5 MO was 128 MB on a cartridge.

Second generation devices (available now) are 230 MB.

Third generation (due out this year?) will be 650 MB.

If they bring the drive price down, could displace floppies as the
basic shirtpocket-transportable medium.

(rdv,95/1/20)

------------------------------
Subject: [6.2.3.9] Nikon 12-inch MO {Brief}
From: Disk

Holds 8 GB on a disk, with a transfer rate of ?>1MB/s.

------------------------------
Subject: [6.2.3.10] Sony 12-inch MO {Brief,New}
From: Disk

Sony also makes a 12" MO. 3.2 GB? (rdv,95/2/7)

------------------------------
Subject: [6.2.3.11] NEC 12-inch MO {Brief,New}
From: Disk

NEC also makes a 12" MO. (rdv,95/2/7)

------------------------------
Subject: [6.2.3.12] Electron-Trapping {None}
From: Disk

------------------------------
Subject: [6.2.4] Dual Function {None}
From: Disk

Capable of using both WORM and Erasable media. Some do the WORM in
firmware -- the media is really rewritable. Others do true WORM.

------------------------------
Subject: [6.2.4.1] IBM {None}
From: Disk

------------------------------
Subject: [6.3] Magnetic
From: Disk

------------------------------
Subject: [6.3.1] 5.25-inch
From: Disk

------------------------------
Subject: [6.3.1.1] Seagate
From: Disk

Seagate's Elite 9 is 9GB -- reports here of backordering, others of
availability. Micropolis due out with an 8GB soon? (94/9/1)

The fastest (in sustained transfer rate) known 5.25" disk drive is the
ST12450W2HP 1.78GB Barracuda drive from Seagate. The Barracuda family
is large, so pay attention to the model number! It runs at 68-113
Mbits/sec., depending on head position (it's ZCAV). Assuming that data
rate is pre-format, and subtracting 20% for the format overhead, that
would be a sustained rate of 6.8-11 MB/sec. Of course, your mileage
WILL vary according to transfer size, locality, etc. (rdv,95/2/7)

------------------------------
Subject: [6.3.2] 3.5-inch
From: Disk

------------------------------
Subject: [6.3.2.1] IBM
From: Disk

The IBM DCMS-310800 Ultrastar2 is 10.8 GB (1GB=10^9) after format, and
its sustained rate is fast -- 8.4-14.2 MB/sec (presumably pre-format,
so subtract 20%). Only 5400 rpm with an 8.9 msec seek time, so
middle-of-the-pack on those numbers. Fast/wide SCSI-2 interface.
(rdv,95/02/14)

------------------------------
Subject: [6.3.3] Bernouli {None}
From: Disk

------------------------------
Subject: [6.3.4] Floptical {Brief}
From: Disk

I believe flopticals use an optical tracking mechanism to improve
ordinary magnetic head positioning and therefore density.

------------------------------
Subject: [6.3.5] Mainframe {Brief}
From: Disk

Mainframe disks are sometimes referred to as SLEDs (Single Large
Expensive Disks). The term DASD (Direct Access Storage Device) usually
refers to a mainframe disk, but is occassionally applied to any hard
disk.

The WWW FAQ contains some information about mainframe CKD disks.

------------------------------
Subject: [6.4] Other
From: Disk

------------------------------
Subject: [6.4.1] Holographic Storage Products {Brief}
From: Disk

Tamarack Storage Devices, Inc, a spin-off from Microelectronics and
Computer Technology Corporation (MCC), is developing with Projectavision Inc.
to produce a product with ten times greater storage densities than magnetic
and 10 to 1000 times faster than floppies, tapes, and CD-ROMS.  First
products expected first quarter 1994.
        (Ref: MCC Collagorations Newsletter, Volume 3, No. 1; Spring 1993)

        ([e-mail])

Also another report of experiments at Stanford recently (8/94).

------------------------------
Subject: [7] RAID {Full}
From: RAID {Full}

The primary functions of a disk array is to increase data
availability, to increase total storage capacity, and to privide performance
flexibility by selectively spreading data over multiple spindles.

Data Protection - As the number of disks on a system increases, the
likelyhood of one failing increases.  Thus, a disk array should be immune
from a single disk drive crash.  Disk mirroring (keeping an exact copy of a
one disk on another) is the simplest, but requires twice the disk capacity
(and associated cost).  Encoding schemes can be used to reduce the redundancy
required to lower ratios.

Storage Capacity is increased by placing many smaller form factor
(5.25 and 3.5-inch) drives onto an intellegent controller which makes all the
drives appear as one drive to the computer system.

Performance can be increased by spreading data over spindles and
performing operations in parallel which allows multiple drives to be working
on a single transfer request.

------------------------------
Subject: [7.1] RAID Levels
From: RAID {Full}

The original taxonomy of RAID levels was published in the SIGMOD paper
by Garth Gibson and Randy Katz in 1988 (see below). The taxonomy
roughly classifies RAID architectures according to the layout of data
and parity information on disks. It is NOT gospel and does NOT cover
every possible architecture (it has been pointed out here that that
would require an N-tuple showing data block addressing, number and
types of parity and ECC information, etc.), but when used properly
provides a vocabulary and establishes a framework for discussion.


        Raid Level 0 - Striping - Data is segmented and split onto multiple
spindles.
                Short Reads - Easily handles multiple simultaneous reads
                Long Reads - Single operation can be split and processed in
parallel
                Short Writes - Easily handles multiple simultaneous reads
                Long Writes - Single operation can be split and processed in
parallel
                Redundancy - None
                Cost - Good (no extra hardware)
        Raid Level 1 - Mirroring - Duplicate data is kept on multiple
splindles
                Short Reads - Faster (shorter latency) since
        resolution can be from any of multiple disks
                Long Reads - Faster since resolution can be from any of
        multiple disks (*)
                Short Writes - Slower since need to write to multiple disks
                Long Writes - Slower since need to write to multiple disks
                Redundancy - Excellent
                Cost - Expensive - at least double the spindle cost
        Raid Level 3 - Data protection disk - mathematical ECC type code
calculated from multiple spindles and stored on another spindle.
                Short Reads - Normal speed (i.e. 1x per-spindle rate)
                Long Reads - Normal speed
                Short Write - Slower due to re-calculating of ECC code
(including reading from other spindles and the ECC write)
                Long Write - slightly slower due to ECC writes, but less
reading required than in short writes (**)
                Redundancy - Excellent
                Cost - only slighly more than no redundancy options
    Raid Level 4??? similar to 3, with block striping instead of byte.
        Raid Level 5 - Striping plus data protection - stripe data across
multiple spindles (as in RAID Level 0) and have data protection calculations
(as in RAID level 3) but don't put all the calculated figures onto one
spindle, but spread it out.
                Short Reads - Normal
                Long Reads - Faster due to parallelism
                Short Write - Slower due to ECC calculation (including
reading and writing)
                Long Write - slighly slower due to ECC writes (**)
                Redundancy - Excellent
                Cost - only slignly more than no reduncancy options

(* should be the same speed as a single spindle)
(** -- should be faster than a single spindle due to parallelism on
write? somebody help me out --rdv)

        Benefits of RAID:
                High data availability (ie, if a single spindle crashes, no
data is lost)
                Increased disk connectivity per system  - since multiple
spindles appear as one spindle to the computer system.
                Large capacity storage in a small footprint -
                Flexibility through intelligent array controllers
                Performance enhancements in some circumstances.


Streamed or Streamified RAID??? (SHMO)

------------------------------
Subject: [7.2] RAID-6
From: RAID {Full}

A two-dimensional disk array parity scheme was described by Randy Katz,
Garth Gibson, and David Patterson (all then with UC Berkeley - Gibson is
now a professor at Carnegie Mellon University) at the 1989 IEEE Compcon
conference. This method had one parity calculated along the disk strings
and another calculated across them. This would increase the
mean-time-to-data-loss by more than 10,000 fold. I am not aware of any
implementations of this configuration.

Storage Technology Corp (STK - Louisville, Colorado) has described a
somewhat similar scheme for their long-delayed Iceberg disk array. This
would have a regular, orthogonal RAID 5 parity across drives along with a
Reed-Solomon encoding on another drive. This is sometimes referred to as
RAID 6 or RAID 5+. STK claims their design will allow failure of ANY TWO
drives - which is beyond the survival capabilities of standard RAID 5.

A RAID 5 which is 'deep' can survive failures in more than one drive so
long as it doesn't lose more than one drive per rank:


        HBA1    HBA2    HBA3    HBA4    HBA5    HBA6    HBA7    HBA8
         |       |       |       |       |       |       |       |
Rank1   Disk1   Disk2   Disk3   Disk4   Disk5   Disk6   Disk7   Disk8
         |       |       |       |       |       |       |       |
Rank2   Disk9   Disk10  Disk11  Disk12  Disk13  Disk14  Disk15  Disk16

        . . . . .   - etc.

Rank4                           .       .       .       .       Disk32


If the above is a RAID 5 then losing drives 5 & 6 will destroy data. If it
is a RAID 6 then it will not. Losing drives 3 and 12 will not disable a
RAID 5 nor a RAID 6.

But RAID 6 will cost more and may have slower performance for small random
writes from having to update more parity data. I think there are clearly
ways to mitigate the parity update perfomance for RAID 6 as well as RAID 5.

--
          Dick Wilmot
          Editor, Independent RAID Report
          [phone]



------------------------------
Subject: [7.3] John O'Brien and RAID-7
From: RAID {Full}

RAID-7 is a marketting term created by Storage Computer, Inc. for what
others here have described as RAID-4 with a write cache. John O'Brien
([e-mail]), (their marketting manager?) frequently posts
here.

His claims of ~10x improvement on I/O rates for VAXes have been shown
to be poorly measured; the change in systems was not simply a
RAID-for-modern-disk swap, but included increasing the CPU power by a
factor of three and eliminating the HSC and old disk technology. He
has also made difficult-to-substantiate claims about the growth and
market success of his company relative to competitors. Thus, wise
advice would be to take everything Mr. O'Brien says with a grain of
salt (not bad advice for dealing with anyone, but especially true for
dealing with vendors).

The debate also appears here frequently as to whether or not you
really WANT your RAID array doing write cacheing; Unix file systems
may depend on specific ordering of writes and otherwise make
assumptions that could leave you in trouble with power or disk
failures. If write ordering is preserved, the danger is somewhat
mitigated.

That said, some posters here are pleased with their RAID7 arrays, and
although comp.arch.storage opinion runs prevalently against Mr.
O'Brien himself (and lately his pal Michael Willett who interestingly
is quoted here from before he worked for Storage Computer), the
possibility exists that the product is worthwhile.

------------------------------
Subject: [7.4] RAID Papers
From: RAID {Full}

A nice collection of RAID papers was published in the Fall, 1991 issue of
_CMG Transactions_. A few more appeared in the December, 1992 _CMG
Proceedings_ and there are 3 RAID papers in the 1993 International
Symposium on Computer Architecture (Published as _Computer Architecture
News 21_, #2, May, 1993 by ACM SIGARCH.

([e-mail], Dick Wilmot, Editor, Independent RAID Report)

Try contacting the RAID project at the University of California, Berkeley.
In the proceedings of the recent IEEE Mass Storage Symposium, Ann Drapeau
and Randy Katz have a paper describing the reults of some investigations
into the use of tape arrays.  I think you can find RAID papers, perhaps
this one, on anon ftp at sprite.berkeley.edu.  Have no address for Ann
Drapeau, but Randy Katz is [e-mail].

The RAID papers are available via anon ftp from
ginger.cs.berkeley.edu:pub/raidPapers

Ann Drapeau's email address is [e-mail].

([e-mail], Mike DeVaney)
([e-mail], Edward K. Lee)

>>I am looking for papers or technical papers on RAID...

You could get that lengthy RAID taxonomy research report from Storage
Computer as mentioned recently on these news groups, by Emailing them at
[e-mail]    Alternatively, their phone number is 603 880 3005.
I do not know if their RAID research report is copyrighted or not.

I believe their executive in charge of RAID activities in Hong Kong would be
John Taylor, the former Wang national accounts director.  They also put
on technical raid seminars which might be of interest to your PhD students,
concentrating on performance enhancements over RAID 3/4/5 (somewhat less than
an order of magnitude, but I have not reviewed their benchmark data.)  The
RAID theory discussed is rather interesting.

([e-mail], Michael Willett)
---------
>> I am looking for papers or technical papers on RAID or other multiple disks
>> storage systems.  Could somebody give me pointers for them?

Here are some papers that I either have read or am looking for:

I don't have copies of this group:

Dishon, Yitzhak; Lui, T.S.; Disk Dual Copy Methods and Their Performance;
  FTCS-18: Eighteenth International Symposium on Fault-Tolerant Computing,
  Digest of Papers p 314-318

Gray, J.N. et. al., Parity Striping of Disk Arrays: Low Cost Reliable
  Storage With Acceptable Throughput, 16th International Conference on
  VLDB (Austrailia, August 1990)

Katz, R.H.; Patterson, D.A.; Gibson, G.A.; Disk System Architectures for
  High Performance Computing; Proc. IEEE v 78 n 2 Feb 1990

Muntz, Richard R.; Lui, John C.S.; Proformance Analysis of Disk Arrays
  Under Failure; Proceedings of the 16th International Conference on Very
  Large Data Bases (VLDB); Dennis Mcleod, Ron Sacks-Davis, Hans Schek
  (Eds.), Morgan Kaufmann Publishers, Aug 1990 pp 162-173

Ng, Spencer; Some Design Issues of Disk Arrays; Compcon '89: Thirty-Fourth
  IEEE Computer Society Internationsl Conference p 137-142
  DISK ARRAYS, STRIPING, SPINDLE SYCHRONIZATION

Ng, Spencer W.; Improving Disk Performance via Latency Reduction; IEEE
  Transactions on Computers v 40 1 Jan 1991 p22-30
  LATENCY REDUCTION, ROTATION LATENCY, DISK PERFORMANCE

Reddy, A.L. Narasimha; Banerjee, Prithviraj; Performance Evalutaion of
  Multiple-Disk I/O Systems; Proceedings of the 1989 International
  Conference on Parallel Processing p 315-318

Here are some good papers on disk arrays with emphasis on RAID:

Chen, Peter M.; Gibson, Garth A.; Katz, Randy H.; Patterson, David A.;
  Evaluation of Redundant Arrays of Disks Using an Amdahl 5890; 1990 ACM
  SIGMETRICS Conference on Measurement & Modeling of Computer Systems p 74-85

Chen, Peter M.; Patterson, David A.; Maximizing Performance in a Striped
  Disk Array; Proceedings of the 17th IEEE Annual International Symposium on
  Computer Architecture p 322-331

Chen, Shenze; Don Towsley; Performance of a Mirrored Disk in a Real-Time
  Transaction System; 1991 ACM SIGMETRICS Conference on Measurement &
  Modeling of Computer Systems p 198-207

Chervenak, Ann L.; Katz, Randy H.; Performance of a Disk Array Prototype;
  ACM SIGMETRICS 1991 Conference Proceedings p 188-197

Menon, J.; Mattson, R.L. and Spencer, N.; Distributed Sparing for Improved
  Performance of Disk Arrays; IBM Research Report RJ 7943 (Jan. 1991)

Patterson, David A.; Chen, Peter; Gibson, Garth; Katz, Randy H.;
  Introduction of Redundant Arrays of Inexpensive Disks (RAID); Compcon 1989:
  Thirty-Fourth IEEE Computer Society International Conference
  p 112-117

Schulze, Martin; Gibson, Garth; Katz, Randy; Patterson, David A.; How Reliable
  is a RAID; Compcon '89: Thirty-Fourth IEEE Computer Society International
  Conference p 118-123


([e-mail], Dan Jones)
--------
>>I am looking for papers or technical papers on RAID...

A good set of the Berkeley papers are available via anonymous FTP.
If I remember, the machine was sprite.berkeley.edu.  Also, an archie
search on "RAID" would probably turn up a nice on-line collection of
information.  (sorry, not at an Internet site to check this right now...)

([e-mail] , Lester Buck)

Further Information:
    %A Garth Gibson
    %A Randy H. Katz
    %T A case for redundant arrays of inexpensive disks (RAID)
    %C Proc. SIGMOD.
    %c Chicago, Illinois
    %D 1--3 June 1988
    %P 109 116
    %k RAID, disk striping, reliability, availability, performance
    %k disk arrays, SCSI, hardware failures, MTTR, MTBF
    %k secondary storage
    %L Jacobson has a copy
    %x Increasing the performance of CPUs and memories will be
    %x squandered if not matched by a similar performance increase in
    %x I/O.  While the capacity of Single Large Expensive Disks (SLED)
    %x has grown rapidly, the performance improvement of SLED has been
    %x modest.  Redundant Arrays of Inexpensive Disks (RAID), based
    %x on the magnetic disk technology developed for personal
    %x computers, offers an attractive alternative to SLED, promising
    %x improvements of an order of magnitude in performance,
    %x reliability, power consumption, and scalability.  This paper
    %x introduces five levels of RAIDs, giving their relataive
    %x cost/performance, and compares RAID to an IBM 3380 and a
    %x Fujitsu Super Eagle.

([e-mail])


------------------------------
Subject: [7.5] R-Squared {Brief}
From: RAID {Full}
Vangard Disk Array for DEC, Sun, HP, IBM RS/6000, SGI and others

Address: 11211 E Arapahoe Rd., Suite 200, Englewood, CO 80112

Phone: [phone], Fax: [phone]

------------------------------
Subject: [7.6] Sun {Brief}
From: RAID {Full}

Sun Microsystems has a new Fibre Channel array that does RAID 0, 1,
and 5. See

http://WWW.Sun.Com/

under the products descriptions. (rdv,94/8/8)

------------------------------
Subject: [7.7] the RAIDbook {Brief,New}
From: RAID {Full}

The RAIDBook, a 100+ page tutorial on RAID technology and the
RAID Advisory Board, is available from Technology Forums, LTD,
of 6931 Glenview Lane, Lino Lakes, MN 55014-1296.

Contact Joe Molina, President of Technology Forums at 612-784-2379 or
612-784-0206.

I've read it, it's decent but a little repetitive. Defines many
low-level terms of interest only to those who need to know the
internals. (rdv,95/2/7)

------------------------------
Subject: [7.8] Software Striping {Brief}
From: RAID {Full}

Silicon Graphics provides software striping of SCSI disks; thus your
host can effectively act as a RAID controller, providing flexibility
and probably reduced price, possibly with a performance penalty in the
form of increased CPU overhead. However, it probably means that it can
spread the I/O load over multiple I/O controllers.

(similar features in other systems? SHMO --rdv)

sdsadmin on the HP 7xx line does raid 0 striping and works well.
this is also apparently possible on the 8xx machines using LVM.
sdsadmin is due to disappear with hpux 10, replaced by LVM.

I believe the Advanced FS on Alphas can also do raid 0.

(mark hahn, [e-mail], 94/11/17)

ATTO Technology    has ExpressStripe, which does software striping on a
Mac.

------------------------------
Subject: [7.9] RAID Vendors {New}
From: RAID {Full}

RAID vendors come and go quickly, OEM each other's equipment, change
names, and other activities that seem aimed at simply obscuring the
market. No list like this could be complete and up to date for long;
I'll gladly take updates.

The November '94 issue of _Advanced Imaging_ has a big article on
storage, primarily RAID arrays, with a pretty comprehensive list. This
table is distilled from that. Most of the info appears to be from the
vendors themselves. Almost all of these are fast/wide SCSI; a few are
Fibre Channel, NuBus, PCI or HiPPI (usually with IPI-3 command set).
Most of these vendors have more than one model, only a few are listed
here. (rdv,95/1/18)

PC = Personal Computer (IBM compatible)
MC = Macintosh
PS = PC Server (Netware, NT et al)
UX = Unix (generic)
PU = Personal Unix
WU = Workstation Unix & workstation servers
MF = mainframe
MI = minicomputer (AS/400)
SU = Supercomputer

FC = Fibre Channel interface (usually SCSI command protocol)

Maker            Model        RAID Levels    Uses
-------------------------------------------------------------------------
AC Technology        Concorde    0,3,5        WU
ADJFILE Systems        Cougar, Tiger    0,1,3,5        ??
AT&T Global Information    Series 3    ??        WU,PS,PC
  Systems -- NCR
BusLogic        DA-x988        0,1,3,5        PC,PU,PS (PCI)
Canary Communications    IDA3500        0,1,3,4,5    ??
Ciprico            6800 Real-Time    ??        ??
            RAID Array
DEC            StorageWorks    0,1,5        ??
            RAID Array 210
Distributed Processing    SmartRAID    0,1,5        PC,PU,PS
  Technology
DynaTek Automation    AddARRAY    0,1        ??
  Systems
Fujitsu Comp. Prod.    DynaRAID    ??        ??
  America
FWB, Inc.        SledgHammer*FT    5        MC
IBM Storage Systems    7137 Disk Array    0,5        WU
Legacy Storage Systems    SmartArray    ??        PC (PCI)
Maximum Strategy    Gen5 Storage    0,1,3,5        SU (HiPPI,FC)
            Server
Mega Driver Systems    MR & MK Series    0,3,5        PC,PU,PS,MC,WU
MicroNet Technology    RAIDbank Plus    0,1,5        PC,PS,MC,PU?
Micropolis        RAIDION,GANDIVA    ??        PC,MC,PS,PU,WU
Microtech Int'l        XLerator    0,1        MC
Mylex            DAC960S        0,1,5,6?,7?    ??
Procom Technology    LANForce-5    0,1,3,5        MC,??
Raidtec            FlexArray IX    0,1,3,5        ??
Recognition Concepts    RDR series    ??        ??
Storage Computer    RAID 7        7?(4?)        ??
Storage Concepts    Concept 910    ??        ??
Storage Tek        Iceberg        ??        MF
XL/Datacomp        9638        5        MI,WU

------------------------------
Subject: [8] Solid State Disk (SSD) Frequently Asked Questions (FAQ)
From: Solid State Disk (SSD) Frequently Asked Questions (FAQ)

*Note: This section is a slightly trimmed and editted version of the
SSD FAQ from Robert at DES ([e-mail]) which I think
he also posts to c.d.sybase. I would take the "up to 1000 times
faster" claim with a grain of salt, though the general info is good.
--rdv, 94/9/15

1) Q. What are solid-state disk emulators?

A. Simply put, solid-state disk emulators are Dynamic Random Access
Memory (DRAM)-based storage devices that appear to the host exactly as a
magnetic rotating disk.  DRAM chips, which are ultra-fast devices
that store data while the system is on, increase data access, thereby
eliminating I/O bottlenecks that constrain overall system performance.

Solid-state disk emulators can be either volatile or non-volatile,
meaning that they are able to retain data when the system is turned off.
DRAM alone is volatile.  Solid-state disk emulators that are designed with an
integrated backup system are non-volatile storage devices; if a power
outage occurs, the user's data is protected by the backup system and will
not be lost. Solid-state disk emulators are volatile when methods for
backing up data are absent.  A power failure will cause data to be
lost on a volatile solid-state disk.

2) Q. How do solid-state disk emulators work?

A. Solid-state disk emulators plug into a computer's I/O controller.
Typical client/server systems use the ANSI-standard SCSI interface on
its I/O controller.  It is plug-and-play because it emulates a
rotating disk.  No special drivers or operating system patches are
required to make it work.  In addition, because there are no moving
parts, seek and rotational latency times are zero, which aids
solid-state disk emulators in performing up to 1000 times faster than
magnetic rotating disk drives.

3) Q. What applications are well-suited for Solid State Disk?

A. In general terms:  1) transaction processing, 2) batch processing, and
3) query or decision support analysis. Many types of application
software can take advantage of the super-fast access times SSD offers.

4) Q. How reliable are Solid State Disks?

A. Based on real world user data from a large SSD site, the actual power
on hours mean-time between failure is greater than 1,000,000 hours. Since
this site has yet to have a failure, the number is likely to go up.

------------------------------
Subject: [9] Other Devices
From: Other Devices

------------------------------
Subject: [9.1] SyQuest Removable Cartridge hard Drives
From: Other Devices
        form factor: 2.5", 42MB
        form factor: 3.5", 105MB, 14msec ave seek, 3600 RPM, ave sustained
transfer rate: 1.3MB/Sec, available in IDE and SCSI versions. Syquest
Technology, Inc., 47071 Bayside Parkway, Frement CA 93438, Phone: 800/245-
2278.

------------------------------
Subject: [9.2] Kalok removable cartridge hard drives
From: Other Devices
        3.5-inch form factor, 250 MB
        Phone: [phone]

------------------------------
Subject: [10] RAIT (Redundant Arrays of Inexpensive Tape)
From: RAIT (Redundant Arrays of Inexpensive Tape)

(6/93)
There are at least two tape array products on the market:

Data General is selling the CLARiiON Tape Array Subsystem comprising
between five and seven 4mm DAT tape drives. Data can be recorded in
RAID-like striping redundancy, mirrored, or in conventional DAT layout.
This unit can provide up to 30GB of unattended contiguous storage. The
tape drives can record at sustained rates of 183 - 732 KB/second each but
customers should expect sustained backup at around 1 megabyte/second of
compressed data after accounting for host overheads. Data General is
working on a seven tape caddie to hold tape sets together. It is essential
that tapes in a RAID group not be separated.

NCR announced a tape array software product for NCR uniprocessors and
System 3450, System 3550 and StarServer Systems running UNIX V R4.2.01.
This tape array software yields faster and more reliable backup of large
database and file servers than with any single tape drive available today
but uses customers existing tape devices. It writes simultaneously to
multiple drives and can use array techniques to recover from loss or
failure in any single tape.

The motivations for tape arrays seems to parallel those for disk arrays:
        -       higher bandwidths
        -       increased reliability

([e-mail], Dick Wilmot, Editor, Independent RAID Report)

(6/93)
Pick up any DEC related trade rags and you can find an ad for an 8mm tape
array.  The ad I just found is by Contemporary Cybernetics and uses two
five GB 8mm drives with compression - they CLAIM to be able to get 50 GB os
storage total - but how many customers have 50 GB worth of 5:1 compressible
data?

Anyway - the ad doesn't mention RAID, but they support RAIDish (!) features
such as striping and mirroring.  It also supports offline tape-to-tape
copy and will automatically cascade onto the second tape when the first
one fills (useful for utilities that can't deal with multi-drive/multi-
volume).

I SEEM to remember someone having something like this with more drives, but
of course I couldn't locate the ad.

I would be really interested in seeing something like this for 3480 since the
transfer rate is already quite high...

([e-mail], Tom Bodoh)

At the Monterey IEEE Mass Storage Conference in April '93, Ann Drapeau
from Randy Katz's group presented a paper on striped tape.

The National Storage Lab High Performance Storage System reportedly
supports striping of removable media in the system software.

(rdv,95/1/13)

Something that came through the newsgroup recently (95/2/5):


Tape Arrays
High Performance tape drive units for large networks and minis.
Fast: up to 4Megabyes/second
High Capacity: from 24Gb on 4mm DATS to 60GB on DLTs; with
autoloaders,up to 616GB
Flexibility: Stripe data across 4 drives, mirror data,
stripe 2/mirror 2 - double your speed while creating an off-site
storage copy; off-line copy; pass-thru mode, etc.
Transparent to your backup software - no changes or retraining
Compatible with all major OSs; including Novell, WindowsNT,
Unix, Sun, HP, Silicon Graphics, VMS, etc.
For More information:
William Wirth
[e-mail]


------------------------------
Subject: [11] RAOT (Redundant Arrays of Other Things :-)
From: RAOT (Redundant Arrays of Other Things :-)

Pinnacle Micro has been advertising what they call the Orray --
essentially RAID done with removable magneto-optical disk drives. They
claim sustained transfer rates up to 8 MB/sec., which seems
implausible given that it's only four drives, and even HP MO drives
are below 2 MB/sec. sustained. Apparently no redundancy in the system
for that configuration (so I guess my ROAT designator is a misnomer),
but it should be generally less necessary for MO than magnetic disk
(drive failures normally don't result in the destruction of data or
media).

        --rdv, 94/7/20
Archive-name: arch-storage/part2
Version: $Header: /home/rdv/comp-arch-storage/RCS/FAQ-2.draft,v 1.15 95/02/18 11:56:38 rdv Exp $
Posting-Frequency: monthly

Rod Van Meter, Joe Stith, and the gang on comp.arch.storage

Information on disk, tape, MO, RAID and SSD can be found in part 1 of
the FAQ.  Part 2 covers file systems, hierarchical storage management,
backup software, robotics, benchmarking, MTBF and miscellaneous
topics.



1.     Standards
1.1.   ANSI X3B5 {None}
1.2.   IEEE Mass Storage System Ref Model (OSSI) {Brief, 11/14/94}
1.3.   ECMA - European Computer Manufacturers Association {None}

2.     Hierarchical Storage Management
2.1.   Unitree {Brief}
2.2.   National Storage Lab {Brief, New}
2.3.   HIARC {New}
2.4.   Epoch (also known as StorageTek's NearNet) {Brief}
2.5.   Zetaco/NETstor {Brief}
2.6.   R-Squared Infinity IFS 2 {Brief}
2.7.   AMASS
2.8.   Tracer XFS {None}
2.9.   Metior
2.10.  NAStore {Brief}
2.11.  DMF {Brief}
2.12.  FileServ {Brief}
2.13.  Cray Research's Open Storage Manager {Brief, New}
2.14.  T-mass {None}
2.15.  Unix HSM Vendor List {New}
2.16.  Non-Unix HSM
2.17.  PC & PC Server Oriented Packages
2.17.1. HP Optical Jukebox Storage Solution
2.17.2. Chili Pepper Software
2.18.  Cheyenne ARCserve {New}

3.     Backup Software
3.1.   PC-Oriented Backup Packages
3.2.   Unix Packages
3.2.1. Spectra Logic Alexandria {New}
3.2.2. ADSTAR Distributed Storage Manager {New}

4.     Robotics (Autochangers, Jukeboxes, Stackers)
4.1.   8mm {Brief}
4.1.1. Exabyte {Brief}
4.1.1.1. EXB-10
4.1.1.2. EXB-10i
4.1.1.3. EXB-10e
4.1.1.4. EXB-120
4.1.2. Lago {Brief}
4.1.3. ACL {None}
4.1.4. Cambridge On-Line Storage {Brief}
4.1.5. Spectra Logic {Brief, New}
4.1.6. Qualstar {Brief,New}
4.2.   3480
4.2.1. StorageTek {Brief}
4.2.2. GRAU {Brief, New}
4.3.   4mm {Brief}
4.3.1. Cambridge On-Line storage {Brief}
4.3.2. Spectra Logic {Brief, New}
4.3.3. HP 4mm {Brief, New}
4.4.   VHS {Brief}
4.4.1. Metrum, 800/METRUM-2
4.5.   Digital Linear Tape (DLT) (Digital Equipment Corp) {Brief}
4.5.1. TZ877 {Brief}
4.5.2. TL820 {Brief}
4.5.3. Metrum
4.6.   D-2
4.6.1. Ampex
4.6.2. Odetics/EMASS
4.7.   Optical Disk (MO,WORM) Libraries
4.7.1. Hitachi 448 GB optical library
4.7.2. HP MO Autochangers
4.7.3. Maxoptix MO Autochangers
4.7.4. Metrum {Brief}
4.7.5. DISC {Brief}
4.7.6. Kodak {Brief, New}
4.8.   CD-ROM Jukeboxes
4.8.1. Pioneer

5.     File Systems
5.1.   NFS {Brief}
5.1.1. NFS V3 {New}
5.2.   AFS {Brief}
5.3.   DFS {Brief}
5.4.   Log based file systems
5.5.   Mainframe File Systems
5.6.   Parallel System File Systems
5.7.   Microsoft Windows NT {Brief}
5.8.   Large Unix File Systems {New}
5.9.   Non-Unix Large File Systems

6.     (Device) Interfaces
6.1.   SCSI {Full}
6.1.1. Single ended vs differential
6.1.2. Asynchronous vs Synchronous Transfers
6.1.3. SCSI-I vs SCSI-II vs SCSI-III
6.1.4. Fast-Wide SCSI
6.1.5. Shared Busses / Performance {Brief}
6.1.6. Cabling/Hot Plugging {Brief}
6.1.7. Third Party Transfers/Separation of Control & Data Paths {Brief}
6.2.   IDE {Brief}
6.3.   IPI {None}
6.4.   HIPPI {Brief}
6.5.   Ultranet {Brief}
6.6.   Ethernet {Brief}
6.7.   FDDI {None}
6.8.   Fibre Channel Standard (FCS) {None}
6.9.   ESCONN {Brief}
6.10.  Serial Bus {None}
6.11.  Multibus, Unibus, Mainframe Channels, and other history {None}

7.     Other
7.1.   Video vs Datagrade tapes {brief, 5/94}
7.2.   Compression {New}

8.     Benchmarking {New}

9.     Mass Storage Conferences

10.    MTBF (Mean Time Between Flareups, er, Failures)

11.    Mass Storage Reports

12.    Appendix
12.1.  Other References
12.2.  Epoch vs Unitree

13.    ORIGINAL CALL FOR VOTES

14.    Original Author's Disclaimer and Affiliation:

15.    Copyright Notice

16.    Additional Topics to be added
------------------------------
Subject: [1] Standards
From: Standards

There's a killer supply of standards, many computer-related, at
http://www-atp.llnl.gov/standards.html Fibre Channel and several
mass-storage-related items can be found there.

------------------------------
Subject: [1.1] ANSI X3B5 {None}
From: Standards

------------------------------
Subject: [1.2] IEEE Mass Storage System Ref Model (OSSI) {Brief, 11/14/94}
From: Standards

Available via ftp://swedishchef.lerc.nasa.gov:mass_store/ as the files
ossiv5.ps{1,2,3}.

The OSSI (Open Storage Systems Interconnection) Reference Model (its
new name) "provides the framework for a series of standards for
application and user interfaces to open storage systems." One of its
prime purposes is to define a common vocabulary. Claiming compliance
with the model at the moment has little practical value as far as
interoperation of different pieces from different vendors goes (which
is one of the ultimate aims of the still-distant standards that may
develop from this model).

------------------------------
Subject: [1.3] ECMA - European Computer Manufacturers Association {None}
From: Standards

------------------------------
Subject: [2] Hierarchical Storage Management
From: Hierarchical Storage Management

HSM systems transparently migrate files from disk to optical disk
and/or magnetic tape, usually robotically accessable.  Then when files are
accessed by a user, they transparently move them back to disk.

Watch for maximum file size limitations, sometimes limited by the
size of the media used.

Some offer integrated backup. Some will manage multiple copies of
files for data reliability.

Some offer integrated migration from other systems (ie, file servers
and/or workstations) to the central location disks, then to the central
location robotics. This generally requires changes to the on-disk file
system format on the migration clients.

An item to watch for is that the file management may be exactly like
Unix -- that is, all files appear to be online, and once they're
deleted, they're gone forever, even though the data may still be on
tape.

All of the subsections here are Unix-compatible (in various flavors)
unless indicated otherwise.

Additional Information:

See also _DEC Professional_, February 1993, Page 40 and _Client/Server
Today_, Dec. '94, p. 60.

The System-Managed Storage Guide by Howard W. Miller, $225 for first
copy, $75 for additional copies for same company available from The
Information Technology Institute, 136 Orchard Street, Byfield, Massachusetts,
01922-1605.

        ([e-mail])

------------------------------
Subject: [2.1] Unitree {Brief}
From: Hierarchical Storage Management

The granddaddy of UNIX HSMs. Developed primarily from an IBM mainframe
product called DataTree at Lawrence Livermore National Laboratories.
Commercialized by a company called DISCOS, then sold to OpenVision.

Many versions exist on different hardware platforms, including a
National Storage Lab (NSL) UniTree commercialized by IBM - Fed
Systems. It's also available on SGI, Convex, and Amdahl hardware, at
least.

        See also "Epoch vs Unitree" in Appendix

For Convex, try


Jim Wilson
214-497-3085
[e-mail]
Business Development
Data Management Applications
Convex Computer Corporation


For most other platforms, call Open Vision at (800)223-OPEN or
[phone].

------------------------------
Subject: [2.2] National Storage Lab {Brief, New}
From: Hierarchical Storage Management

NSL is an industry consortium (American companies only) that has a
version of Unitree, and is creating their own new High Performance
Storage System.

HPSS, among other features, supports striping of removable media. Some
of the work is being done at LLNL, where UniTree was originally
developed.
There's a good overview reachable at
http://www.ccs.ornl.gov/HPSS/HPSS.html.

(rdv,95/1/12)

------------------------------
Subject: [2.3] HIARC {New}
From: Hierarchical Storage Management

?SHMO. I've heard of this but don't know anything about it.

------------------------------
Subject: [2.4] Epoch (also known as StorageTek's NearNet) {Brief}
From: Hierarchical Storage Management
        See also "Epoch vs Unitree" in Appendix

------------------------------
Subject: [2.5] Zetaco/NETstor {Brief}
From: Hierarchical Storage Management

        NETstor can be reached at [e-mail]

        NETstor, Inc. (formerly Zetaco, Inc.) is a leading provider of
hierarchical online mass-storage systems for open systems.  Primarily NFS
accessable systems with magnetic disks and optical-disk libraries.  They have
marketing agreements with Digital Equipment Corp, and Hewlett-Packard.

        ([e-mail])

------------------------------
Subject: [2.6] R-Squared Infinity IFS 2 {Brief}
From: Hierarchical Storage Management

        Contact: Steve Wine, Manager, Mass Storage Products, R-Squared, 11211
East Arapahoe Rd, Englewood, CO  80112, 303/799-9292 or FAX [phone]

------------------------------
Subject: [2.7] AMASS
From: Hierarchical Storage Management

From Advanced Archival Products. Supports a huge range of devices,
autochangers, and operating systems. Block-based movement of data
between the hard disk cache and tape or optical tertiary storage.
Systems run from a few gigabytes up to at least 12 TB, with prices
dependent on capacity. New versions allow multiple cache disks. Slips
right in to the VFS layer and looks like a normal Unix file system,
with the plusses and minuses that entails. No file versioning or
multiple copies yet. File creation is an Achilles' heel on
performance. Since it's block based, files can be larger than a piece
of media. Separate product DataMgr will migrate files from client
machines to the AMASS server automatically (with FS changes, of
course).

------------------------------
Subject: [2.8] Tracer XFS {None}
From: Hierarchical Storage Management

------------------------------
Subject: [2.9] Metior
From: Hierarchical Storage Management

Metior (pronounced like meteor) is targetting an incredibly broad
market, from laptops with removable media through supercomputers, with
prices from $650(!) to $118K. They handle multiple coordinated copies,
so off-site backup can be automatic. Can do migration for client
machines (with appropriate software licenses and changes to the file
system). The hierarchy seems to be extremely flexible, variable on a
per-user or per-group basis. Machines without client licenses can
mount the Metior FS using NFS. Runs on Suns, SGI, and HP 9000/700. ANT
is new, and they've only got a handful of customers so far, but it
looks _very_ interesting.

(info from [e-mail], written by rdv, so it's my fault if it's
not accurate) (rdv,94/7/7)

More information available on the WWW FAQ version.

Automated Network Technologies
3333 South Bannock Street, Suite 945
Englewood, CO 80110   USA
Phone [phone]
FAX [phone]
Email [e-mail]


------------------------------
Subject: [2.10] NAStore {Brief}
From: Hierarchical Storage Management

NAStore is a Unix migrating file system developed by the Numerical
Aerodynamic Simulation program at NASA Ames. It is available through
NASA's software distribution agency, COSMIC. It currently runs only on
Convex with 34x0 cartridges and Storage Tek robots. Looks like a local
file system to users of the Convex.

Info on NAStore can be found on the web at
http://chuck.nas.nasa.gov/NAStore/NAStore.html

        COSMIC's address is :
        University of Georgia
        382 East Broad Street
        Athens, Georgia, 30602-4272, US
        011-706-542-3265
        [e-mail]

For more information on NAStore, contact John Lekashman, [e-mail].
(info from Bill Ross, [e-mail], 94/9/15)

------------------------------
Subject: [2.11] DMF {Brief}
From: Hierarchical Storage Management

Cray Research's Data Migration Facility.

------------------------------
Subject: [2.12] FileServ {Brief}
From: Hierarchical Storage Management

From E-Systems. Works with the E-Systems ER-90 (D-2) tape drive and
Odetics robots, as well as 3480 with the Storage Tek ACS 4400. Runs on
Convexes (only?). Supports multiple copies of files. Retrieves only
necessary info from tape to disk before completing request.

------------------------------
Subject: [2.13] Cray Research's Open Storage Manager {Brief, New}
From: Hierarchical Storage Management

They have some agreement with Legent Corporation. OSM runs on Sparc
machines, including the Cray Superservers. Price ranges from $500 to
$5,000, which is very cheap for HSM. However, it might only be capable
of migrating among disks -- I don't see any mention of autochangers.
(rdv, 94/12/9)

------------------------------
Subject: [2.14] T-mass {None}
From: Hierarchical Storage Management

------------------------------
Subject: [2.15] Unix HSM Vendor List {New}
From: Hierarchical Storage Management

This list is adapted from _Client/Server Today_, Dec. '94, with some
of my own additions. All the phone numbers are USA (apologies to
international readers for the 800 numbers, but they're all I've got).
I don't know anything about some of these companies; I suspect some of
them work with HSM from other vendors rather than their own packages.

I've indicated on the list various reports of companies OEMing from
each other; this is not out of disrespect for the work involved in
OEMing/supporting or porting such complex software, but an attempt to
divide the HSM vendors into "families" with similar capabilities
(occassionally on very disparate platforms).

Vendor                    Product        Contact
------                    -------        -------
Advanced Archival Products        AMASS        [phone] *
Advanced Software Concepts (ASC)            [phone]
Alphatronix                ASC        [phone]
Artecon                    ASC        [phone]
AT&T CommVault                DataMigrator    [phone]
Automated Network Technologies (ANT)    Metior        [phone] *
Computer Associates International            [phone]
Computer Upgrade                    [phone]
Convex Computer                UniTree        [phone] *
COSMIC (NAStore)                    [phone] +
Cray Research                DMF                  ?*
Digital Equipment (DEC)            NETstor        [phone]
Dorotech                        [phone]
Epoch Systems                        [phone] *
E-Systems                FileServ              ?*
File Tek                        [phone]
Fujitsu Computer Products of America    OSM        [phone]
Hewlett-Packard                NETstor        [phone]x8509
HIARC                            [phone]
IBM                    UniTree        [phone]
Introl                            [phone]
Large Software Configurations (LSC)            [phone]
Legent                    $OSM        [phone]
National Storage Lab (NSL)         HPSS                  +*
NETstor (Cheyenne)            $NETstor    [phone]
OpenVision                UniTree        [phone] *
Qstar Technologies                    [phone]
Raxco                            [phone]
Software Partners/32                    [phone]
Storage Technology (STK, StorageTek)            [phone]
T-mass                                           ?
Tracer XFS                                  ?

* = Info elsewhere in FAQ
+ = not commercial product
? = no contact info
$ = original developer (no mark indicates OEM)

------------------------------
Subject: [2.16] Non-Unix HSM
From: Hierarchical Storage Management

DEC's old Tops-20 OS supported offline files, and would generate an
automatic request to the operator to mount a tape when the user
accessed the file. When you listed a directory, it would show you
which files were online and which off.

DEC's OpenVMS has some sort of support for this now. VMS 6.1 supports
"shelved" files.

There is also the product Virtual Branches, from Acorn Software, which
does HSM for MO and CD-ROM for OpenVMS.


Acorn Software, Inc.
179 Great Road, Suite 104
Action, MA  01720
voice:  [phone]
fax:    [phone]
Internet:  [e-mail]


For Windows NT:

Try:

Avail Systems
4760 Walnut St
Boulder, CO  80301
voice: +1.303.444.4018
  fax: [phone]

[e-mail] (Dave Skinner) (95/2/12)



------------------------------
Subject: [2.17] PC & PC Server Oriented Packages
From: Hierarchical Storage Management

------------------------------
Subject: [2.17.1] HP Optical Jukebox Storage Solution
From: Hierarchical Storage Management
        Netware 3.11 based, up to 10.4 Gigabytes, includes model 10LC optical
jukebox which has one drive and 16 disks each with 650 MB formatted capacity.
Hewlet-packard (Palo Alto, CA) 800/826-4111.

------------------------------
Subject: [2.17.2] Chili Pepper Software
From: Hierarchical Storage Management

A company from Atlanta, GA named Chili Pepper Software (404-339-1812)
and 3M have gotten together in some fashion to make HSM software for
PCs using QIC. (rdv, 94/9/5)

------------------------------
Subject: [2.18] Cheyenne ARCserve {New}
From: Hierarchical Storage Management

Runs on Netware servers. Transparent to most clients, but has a neat
feature: if you use a special TSR and DLL on client PCs, when it has
to retrieve a file from secondary or tertiary storage, it can give you
an estimated retrieval time and the option to abort. [phone],
[phone].
(rdv,95/02/14)

------------------------------
Subject: [3] Backup Software
From: Backup Software

Backup software usually provides some form of management of files,
tapes, and autochangers. Retrieval of files is not automatic (as in
true HSM). These are designed to allow you to recover from disk or
file system failures, and to recover files accidentally (or
maliciously) deleted or corrupted. Some work in conjunction with HSM
systems, which are often vulnerable to the latter class of problems.

I've concentrated here on backup software that supports various
autochangers, as this is of more interest to people in this group than
standalone software for backing up one hard disk onto one tape.

------------------------------
Subject: [3.1] PC-Oriented Backup Packages
From: Backup Software

I don't think any of the PC operating systems come with tape support
built in, so you have to have some 3rd party software to work with
tape. This short list is primarily oriented toward PC servers.
It's partly derived from _PC Magazine_, March 29, 1994, pp. 227-272.

Arcada Software - Storage Exec.        (NT)
Avail                    (NT)
Cheyenne Software - ArcServe        (Netware)
Conner Storage Systems - Backup Exec    (Netware)
Emerald Systems - Xpress Librarian
Fortunet - NSure NLM/AllNet
Legato - NetWorker            (Netware)
Mountain Network Solutions - FileSafe
NovaStor                (Netware)
Palindrome - Network Archivist        (Netware, OS/2, Windows)
Palindrome -Backup Director
Performance Technology - PowerSave    (Netware)
Systems Enhancement - Total Network Recall

{Under Construction}(SHMO)

------------------------------
Subject: [3.2] Unix Packages
From: Backup Software

Some people claim "Unix tape support is an oxymoron," so there's a big
market in outdoing tar, dump, dd and cpio.

APUnix - FarTool
Cheyenne - ArcServe (see under PCs, above)
Dallastone - D-Tools
Delta MicroSystems (PDC) - BudTool
Epoch Systems - Enterprise Backup
IBM - ADSM (Adstar Distributed Storage Manager)
Hewlett Packard - OmniBack II
Legato - Networker
Network Imaging Systems
Software Moguls - SM-arch
Spectra Logic - Alexandria
Workstation Solutions

{Under Construction}(SHMO)

------------------------------
Subject: [3.2.1] Spectra Logic Alexandria {New}
From: Backup Software

Spectra Logic makes 4mm & 8mm autochangers, but this software supports
other autochangers as well. Has a nice feature that it claims to be
capable of backing up live Oracle, Informix and Sybase databases.
email [e-mail]. (rdv,95/2/14)

------------------------------
Subject: [3.2.2] ADSTAR Distributed Storage Manager {New}
From: Backup Software

Runs on everything from OS/2, AIX and OS/400 to VSE/ESA, MVS and VM
providing backups for virtually everything you can think of in PCs and
workstations. (800)IBM-3333 or anonymous ftp to index.storsys.ibm.com.
(rdv,95/2/14)

------------------------------
Subject: [4] Robotics (Autochangers, Jukeboxes, Stackers)
From: Robotics (Autochangers, Jukeboxes, Stackers)

I use the term "robotics" to refer to access to multiple removable
volumes by a fewer number of drives without a person.  This includes
sequential stackers, as well as random access robotics.

A stacker typically is capable of taking (literally) a stack of tapes
and putting them into the drive one at a time, in order. No random
access to specific tapes, as with a full-function autochanger.
Stackers typically are limited to 8-10 cartridges, and are used by
people whose backups have exceeded the size of one cartridge.

------------------------------
Subject: [4.1] 8mm {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers)

------------------------------
Subject: [4.1.1] Exabyte {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers)
Phone: 800/EXABYTE, 1685 38th st, Boulder, CO 80301, Fax [phone].

------------------------------
Subject: [4.1.1.1] EXB-10
From: Robotics (Autochangers, Jukeboxes, Stackers)
        Ten cartridges, one full-height drive

Original 10 cartridge robot.  No robotic intelligence, when one tape
comes out, the robot mounts the next tape in sequence (i.e. a kind of
stacker).  Button selectable to loop back to the first tape or to stop
at the end.

------------------------------
Subject: [4.1.1.2] EXB-10i
From: Robotics (Autochangers, Jukeboxes, Stackers)
        Ten cartridges, one full-height drive.

Released shortly after the EXB-10.  Includes SCSI attachment to
robotics.  Now nearly replaced by the EXB-10e.

------------------------------
Subject: [4.1.1.3] EXB-10e
From: Robotics (Autochangers, Jukeboxes, Stackers)

Ten cartridges, one full-height drive.

Announced around 4/93.  Includes better controll panel and display
than EXB-10i.  Drive mounted horizontal and tape magazine at slight angle
(rather than visa versa in EXB-10i).

------------------------------
Subject: [4.1.1.4] EXB-120
From: Robotics (Autochangers, Jukeboxes, Stackers)

Holds 120 8mm cartridges, up to four full-height drives.

------------------------------
Subject: [4.1.2] Lago {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers)

 Holds 54 8mm tape cartridge in a carousel with 2 8mm drives.


        Lago can be reached at 800/866-LAGO
                LAGO Systems
                Address: 151 Albright Way
                Los Gatos, CA 95030-9973


------------------------------
Subject: [4.1.3] ACL {None}
From: Robotics (Autochangers, Jukeboxes, Stackers)

------------------------------
Subject: [4.1.4] Cambridge On-Line Storage {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers)
        Sixty and 240 GB libraries, 713/981-3812

------------------------------
Subject: [4.1.5] Spectra Logic {Brief, New}
From: Robotics (Autochangers, Jukeboxes, Stackers)

Spectra Logic makes SCSI-controlled 8mm and 4mm (DAT) autochangers.
One to four drives, with 20 to 60 slots. Capacity currently up to 600
GB of DDS-2 (4mm) or 300 GB 8mm. Early models (STL-6000 & STL-8000)
were a rotating carousel. Newer ones use an arm and the tapes don't
move.

Supported by a variety of software vendors. List prices of $9K
(Spectra 4000/20 slots, one DDS-2 drive) to $31K (60 slots with four
drives and barcode support) including drives.

They also make a thing called TapeFrame, which consists of several of
their autochangers working in conjunction, with capacities up to 2.2
TB.

U.S.: 1-800-833-1132 or 303-449-6400

(Britt Terry, [e-mail], 95/1/12)

See also under backup software.

------------------------------
Subject: [4.1.6] Qualstar {Brief,New}
From: Robotics (Autochangers, Jukeboxes, Stackers)

Makes 8mm libraries that hold 10 to 120 cartridges and 2 to 6 drives.
tel:[phone] fax:[phone] (rdv,95/2/14)

------------------------------
Subject: [4.2] 3480
From: Robotics (Autochangers, Jukeboxes, Stackers)

------------------------------
Subject: [4.2.1] StorageTek {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers)

Storage Tek makes huge autochangers, referred to as silos, round and
several (~5) meters in diameter. They hold 6,000 3480-style tapes. At
original 3480 densities, that's only 1.2 TB per silo, but capacities
have gone up to (I think) 800 MB/cartridge, and are poised for a HUGE
jump if Storage Tek gets their Redwood tape drive finished (in beta
test, 12/94), up to 20 GB/cartridge, 120 TB/silo.

STK also OEMs a 3480 autochanger from Odetics. Holds ~260 cartridges,
I think, in rotating drum, with room for ?2? tape drives above it.
(rdv,95/1/12)

------------------------------
Subject: [4.2.2] GRAU {Brief, New}
From: Robotics (Autochangers, Jukeboxes, Stackers)

Grau, a German manufacturer, makes high-end, very large capacity
mixed-media autochangers known as the ABBA series, targetted I believe
primarily at the IBM mainframe market. I know they support 3480-format
cartridges, but I'm not sure what other media (rdv,94/11/7).

------------------------------
Subject: [4.3] 4mm {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers)

------------------------------
Subject: [4.3.1] Cambridge On-Line storage {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers)
        Libraries of 120 and 40 GB, 713/981-3812

------------------------------
Subject: [4.3.2] Spectra Logic {Brief, New}
From: Robotics (Autochangers, Jukeboxes, Stackers)

Spectra Logic makes SCSI-controlled 8mm and 4mm autochangers. See
above under 8mm autochangers.

------------------------------
Subject: [4.3.3] HP 4mm {Brief, New}
From: Robotics (Autochangers, Jukeboxes, Stackers)

I think HP makes their own 4mm autochangers.

------------------------------
Subject: [4.4] VHS {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers)

------------------------------
Subject: [4.4.1] Metrum, 800/METRUM-2
From: Robotics (Autochangers, Jukeboxes, Stackers)

Autochangers for their VHS-based high-capacity (20GB, 2 MB/sec.) tape
drive. They now have a stacker available for standalone drives.

Library of 960 GB (RSS-48b) holds 2 drives and 48 cartridges in a
rotating drum.

Library of 12 TB (RSS-600b) holds 5 drives and 600 cartridges in less
than 20 square feet of floor space. The tapes are held in rotating
drums on each side, with the drives in a rack in between.

OEMs through Convex, IBM, and a host of resellers. Integrated with
various backup and HSM packages, including UniTree from Convex & IBM,
and AMASS from AAP.

See Metrum also under MO and DLT autochangers.


Metrum Information Storage
4800 E. Dry Creek Rd.
Littleton, CO 80122
[phone]
[phone]
[phone] (fax)


------------------------------
Subject: [4.5] Digital Linear Tape (DLT) (Digital Equipment Corp) {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers)
        T* names are DEC's names, DLT2* names are OEM names.

------------------------------
Subject: [4.5.1] TZ877 {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers)

        One TZ87 tape drive, 7 cartridges, each 10GB native
        Presumed to be the same as the DLT2700 library.
        Ref: Digital's Customer Update, March 14, 1994


------------------------------
Subject: [4.5.2] TL820 {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers)

        Holds 3 TZ87 tape drives, 264 catridges, five libraries attachable
        Presumed to be Odetics made (714/774-5000)
        About $150K U.S.
        Ref: Digital's Customer Update, March 14, 1994

------------------------------
Subject: [4.5.3] Metrum
From: Robotics (Autochangers, Jukeboxes, Stackers)

At Comdex '94 in Vegas, Metrum introduced the D-900 (900 cartridges,
up to 20 drives, 9TB uncompressed for DLT-2000) and D-360 (360
cartridges, up to 8 drives, 3.6 TB uncompressed for DLT-2000) DLT
autochangers. There is an expansion unit with 480 cartridges and no
drives. Up to eight D-360 or D-480 units can be connected via
passthrough. They also introduced 28 and 60 cartridge DLT
autochangers. Customer shipments starting in early '95. See above
under VHS for contact info.

------------------------------
Subject: [4.6] D-2
From: Robotics (Autochangers, Jukeboxes, Stackers)

------------------------------
Subject: [4.6.1] Ampex
From: Robotics (Autochangers, Jukeboxes, Stackers)
Ampex makes their own autochangers for the DST DD-2 tape drive (see
part 1 of the FAQ).

DST 410 Automated Cartridge Library:
Up to 1.2 terabytes capacity (uncompressed) in 7 square feet of floor space.
All 3 cartridge (cassette) sizes supported - 25, 75, 165 gigabytes
(uncompressed).
SCSI Medium Changer Commands or Ethernet NetSCSI protocol.
Console mounted configuration.
Single unit price:  $150K.

DST 810 Automated Cartridge Library:
Up to 6.4  terabytes (uncompressed) in 21 square feet of floor space.
Robotic performance of 600 cartridge exchanges per hour.
Average access time to any file less than 30 sec. (including cartridge
exchange, drive load and search to data).
1 to 4 tape drives per library.
Ethernet NetSCSI protocol robotics control.
Starting single unit price:  $300K.

([e-mail], 94/12/23)

------------------------------
Subject: [4.6.2] Odetics/EMASS
From: Robotics (Autochangers, Jukeboxes, Stackers)

Odetics makes a thing called a DataTower that holds ~250 S-size D-2
cartridges. It's sold through EMASS for use with the ER-90 (the
Ampex/EMASS D-2 drive). It's a small silo that sits in front of one
rack of drives.

They also make an expandable library known as the DataLibrary, with a
maximum capacity of ten petabytes(!) (ten million gigabytes). A robot
handler runs on a track down an aisle lined with cartridges, and tape
drives at one (both?) end(s) of the aisle. I think the aisles can vary
in length, and they can be lined up next to each other and I believe
cartridges will pass between them.

------------------------------
Subject: [4.7] Optical Disk (MO,WORM) Libraries
From: Robotics (Autochangers, Jukeboxes, Stackers)

Several other Japanese manufacturers make optical libraries, I think,
mostly in support of their own drives. (SHMO)

------------------------------
Subject: [4.7.1] Hitachi 448 GB optical library
From: Robotics (Autochangers, Jukeboxes, Stackers)
12-inch worm, up to 7GB per platter, 2-4 drives, additional cartridge
expansion unit increases capacity 560 GB to 1,008 GB.
Drive rates up to 2.22 MB/sec.
Phone: 800/HITACHI

------------------------------
Subject: [4.7.2] HP MO Autochangers
From: Robotics (Autochangers, Jukeboxes, Stackers)

Makes several models, from 16 disks and one drive up to 144 disks and
?4? drives. These are very popular.

------------------------------
Subject: [4.7.3] Maxoptix MO Autochangers
From: Robotics (Autochangers, Jukeboxes, Stackers)

Makes several models in the MaxLyb series, the 52, 120 and 180, which
correspond to the capacity in gigabytes for 1.3 GB drives. They hold,
respectively, 2 (52), 2 or 4 (120) and 2, 4 or 6 (180) drives.

They also have a fairly mysterious thing called the Axxis^26, a "high
speed network file retrieval & backup server," which is obviously an
MO autochanger, apparently bundled with a license for Palindrome
Backup Director, suitable for attaching to your Netware file server?

tel: [phone]
fax: [phone]

(rdv,95/02/14)

------------------------------
Subject: [4.7.4] Metrum {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers)

Now has the OSS-626, which holds 450-626 disks and 2-24 full-height HP
drives. See above under VHS for contact info.

------------------------------
Subject: [4.7.5] DISC {Brief}
From: Robotics (Autochangers, Jukeboxes, Stackers)

Makes large libraries (up to ~1 TB with passthrough); rumored to be in
financial trouble.

------------------------------
Subject: [4.7.6] Kodak {Brief, New}
From: Robotics (Autochangers, Jukeboxes, Stackers)

Kodak makes their own autochangers for their large (?12"?) optical
drive.

------------------------------
Subject: [4.8] CD-ROM Jukeboxes
From: Robotics (Autochangers, Jukeboxes, Stackers)

------------------------------
Subject: [4.8.1] Pioneer
From: Robotics (Autochangers, Jukeboxes, Stackers)

From: [e-mail] (Mike Caplinger)
Subject: driver software for Pioneer DRM-5004X CDROM jukebox
Date: Tue Aug 23 10:09:00 PDT 1994
Organization: UTexas Mail-to-News Gateway
Lines: 13

Pioneer recently announced their DRM-5004X CDROM jukebox, which has
four quad-speed drives and holds 500 CDs for under $20,000.

        Mike Caplinger
        [e-mail]

------------------------------
Subject: [5] File Systems
From: File Systems

This topic is also discussed frequently in comp.os.research.

------------------------------
Subject: [5.1] NFS {Brief}
From: File Systems

The Network File System, originally developed by Sun Microsystems and
now pretty standard in the Unix world. V2, the common version,
supports single files only up to 2^32 (4GB) bytes. I'm not sure if
there are any limits to a file system size under NFS, other than those
imposed by the client and server OSes (SHMO).

NFS is defined in RFC 1094. I don't think V3 is standardized yet.

There is at least one newsgroup devoted specifically to NFS.

------------------------------
Subject: [5.1.1] NFS V3 {New}
From: File Systems

NFS V3 supports 64-bit files.

The first implementation was from Digital with DEC OSF/1 V3.0 for
Alpha AXP. Silicon Graphics supports it on IRIX 5.3. Cray will support
it on UNICOS 9. I don't know about other vendors but I have heard
rumours that the releases coming in the second half of 1995 will
support it.

Further information on NFS V3 can be found from
ftp://gatekeeper.dec.com/pub/standards/nfs/NFS3.spec.ps.Z

([e-mail], 95/1/22)

------------------------------
Subject: [5.2] AFS {Brief}
From: File Systems

The Andrew File System (SHMO). Allows naming of files worldwide as if
they were a locally-mounted FS (from cooperating clients, of course).

------------------------------
Subject: [5.3] DFS {Brief}
From: File Systems

Another remote file system protocol that supports large files. I don't
know anything about it, or if any implementations really exist yet.

------------------------------
Subject: [5.4] Log based file systems
From: File Systems

Further Information:
    %z InProceedings
    %K hpdb:Rosenblum91
    %s [e-mail] (Thu Oct 17 11:12:07 1991)
    %A Mendel Rosenblum
    %A John K. Ousterhout
    %y UCBCS.
    %T The design and implementation of a log-structured file system
    %C Proc. 13th SOSP.
    %c Asilomar, Pacific Grove, CA
    %p ACM. SIGOPS
    %D 13 Oct. 1991
    %P 1 15
    %x This paper presents a new technique for disk storage management
    %x called a log-structured file system.  A log-structured file system
    %x writes all modifications to disk sequentially in a log-like
    %x structure, thereby speeding up both file writing and crash
    %x recovery.  The log is the only structure on disk; it contains
    %x indexing information so that files can be read back from the log
    %x efficiently.  In order to maintain large free areas on disk for
    %x fast writing, we divide the log into segments and use a segment
    %x cleaner to compress the live information from heavily fragmented
    %x segments.  We present a series of simulations that demonstrate the
    %x efficiency of a simple cleaning policy based on cost and benefit.
    %x We have implemented a prototype log-structured file system called
    %x Sprite LFS; it outperforms current Unix file systems by an order of
    %x magnitude for small-file writes while matching or exceeding Unix
    %x performance for reads and large writes.  Even when the overhead for
    %x cleaning is included, Sprite LFS can use 70% of the disk bandwidth
    %x for writing, whereas Unix file systems typically can use only
    %x 5--10%.

([e-mail])

------------------------------
Subject: [5.5] Mainframe File Systems
From: File Systems

The WWW FAQ contains some information about mainframe file systems.

------------------------------
Subject: [5.6] Parallel System File Systems
From: File Systems

This discussion comes up occassionally on comp.arch and
comp.os.research. I don't know which newsgroups/mailing lists the PIO
(Parallel I/O) people hang out in, but it doesn't seem to be here.
They show up occassionally in comp.sys.super and comp.parallel.  They
do have their own conferences, though.

The important work seems to be going on with the supercomputing gang
-- LLNL, CMU, Caltech, UIUC, Dartmouth, ORNL, SNL, etc. Work is also
being done by the parallel database community, including vendors such
as Teradata.

A paper presented at the ACM International Supercomputing Conference
in 1993 showed what to me seemed to be pretty appalling performance
for reading data and distributing it to multiple processors on an
Intel Delta supercomputer (sorry I don't have the reference in front
of me). (rdv, 94/8/12) The paper is old, now, and the Intel guys say
they have improved performance to up to 130 MB/sec. on the new Paragon
using their Parallel File System (PFS).

There is a good web site on parallel I/O at Dartmouth:
http://www.cs.dartmouth.edu/pario.html

------------------------------
Subject: [5.7] Microsoft Windows NT {Brief}
From: File Systems


I seem to recall that NT supports 64-bit file systems for its own
native file systems? Anybody know for sure (SHMO)? (rdv, 94/8/24)

------------------------------
Subject: [5.8] Large Unix File Systems {New}
From: File Systems

There is now an industry group working on standardizing an API for
files larger than 2 GB (the max size normally supported on most Unix
systems). More info as I get it. The WWW-enabled can have a look at
http://www.sas.com:80/standards/large.file and see the various
proposals on the table.

Note that it is VERY easy to confuse whether an OS supports _files_
larger than 2 GB or _file systems_ larger than 2 GB. My table lists
some of both (thanks to [e-mail] (Benjamin Z.  Goldsteen),
Ed Hamrick ([e-mail]) and Peter Poorman ([e-mail])
for much of this information).


It is straightforward for systems with 64-bit integers to support
64-bit files; for systems with 32-bit integers it is more complex. On
most 32-bit systems the offsets passed around inside the kernel (most
importantly, at the VFS layer) the file offsets and sizes tend to be
passed as 32-bit (signed) integers, meaning no files >2^31.

On most systems, the argument to lseek is of type off_t, which (on
SunOS and Linux, and plausibly on OSF/1 and others) is declared in a
header file as "typedef long off_t;".

For clients to really have access to large files, three pieces are
required: local FS support, an appropriate network protocol, and
server support for 64-bit FSes. For FTP access, I believe _literally_
inifinitely large files are possible, but I'm not sure(SHMO). For NFS
access, NFS V2 supports only 2GB files. NFS V3, just becoming
available now, supports full 64-bit files, I believe (anybody have a
reference to the docs? RFC? SHMO). With the notable exception of
Unitree (which does not use, depend on, or appear as, a local FS on
the server), server support for 64-bit files is provided only when the
server's own local FSes are 64-bit.

Even for the systems that _do_ support large files, not all are
programmer or user-transparent for supporting large files. UniCOS is,
OSF/1 is, ConvexOS is not (there are two system calls, lseek and
lseek64, with 32-bit and 64-bit file offsets, respectively, though the
Fortran interface is transparent).

This brings up the related issues.  A complete large files implementation
needs not only the system calls, but also the stdio library and the runtime
libraries for the languages (Fortran, Cobol,...).  Further, system utilities
(sed, dd, etcetera) need to be capable of dealing with large files.

(It has been pointed out that the GNU C compiler runs on most of these
machines, so it is possible to use "long long" as a 64-bit int on
them, but what matters for file systems is the system compiler.)

Here's the start of a table on these. Really such a simple table can't
do the problem justice, but it'll give you an idea. Keep in mind that
many of these systems support many file system types; I've listed only
the most interesting so far from this point of view. I'd like to flesh
it out more completely, though.


1 GB = 2^30, 1 TB = 2^40, 1 PB = 2^50, 1 EB = 2^60
NYR = Not Yet Released

OS/hardware        64-bit C    max    max    NFS    info
            datatype    par-    file    V3    updated
                    tition    size    sup
                    size    (bytes)
UniCOS (Cray vector)    int, long    ?    8 EB?    ?    8/94
ConvexOS        long long    1 TB    1 TB    N    9/94
Alpha AXP OSF/1 V3.0
    AFS        long        128 GB    16 TB    8/94    9/94
Paragon OSF/1        ?        8 EB*    8 EB    N    2/95
UTS (Amdahl)        ?        ?    8 EB?    ?    8/94
HP/UX 9 (HP 9xxx)    ?        4 GB    ?    ?    8/94
Silicon Graphics
    IRIX 5.2 EFS    long long    8 GB    2 GB    N    9/94
    IRIX 6.0 EFS    long        8 GB    2 GB    N    9/94 (NYR)
    IRIX 5.3 XFS    ?long long?    ?    ?TB?    Y    9/94 (NYR)
AIX (IBM RS/6000)
    4.1 JFS        long long    64 GB    2 GB    N    8/94
Solaris 2.x (Sun Sparc)    long long    1 TB    2 GB    (soon?)    9/94
BSD 4.4            long long    ?    8 EB?    ?    8/94
Linux            long long    1 TB    2 GB    ?    9/94
DG/UX 5.4        long long    2 TB    2 GB    ?    9/94
Alliant Concentrix    long long    ?>2 GB    ?>2 GB    N    9/94 (dead)

* The Paragon PFS (Parallel File System), as I understand it, parallelizes
access to the files; each partition striped across is limited to 2GB, so
really the max partition size is 2GB * # of disks that can be attached.

A slightly more detailed
description of certain implementations
is available with the WWW version.

------------------------------
Subject: [5.9] Non-Unix Large File Systems
From: File Systems

(info about non-Unix large FSes also welcome; SHMO)

OpenVMS (any version) supports 2TB files (32-bit unsigned block
number, 9-bit offset) through its RMS interface (still limited to 2GB
through the C run-time library), but file systems are limited to ~7GB
(as of Open AXP 1.5 and OpenVMS VAX 6.0 the max volume size has been
bumped to 1 TB). (from a friend, rdv, 94/8/26, and Rod Widdowson,
Filesystems group, OpenVMS engineering, Scotland).

------------------------------
Subject: [6] (Device) Interfaces
From: (Device) Interfaces

------------------------------
Subject: [6.1] SCSI {Full}
From: (Device) Interfaces

SCSI is the Small Computer System Interface. It is standardized by
ANSI X3T9.2. It is mostly aimed at storage devices, with command sets
defined for disks, tapes, and autochangers, but also includes
communications devices, printers, and scanners.

It's daisy-chained, with a maximum of eight devices (including the
host computer) on a single narrow bus (there are non-standard schemes
for 16 devices on a wide bus). Any device can be an initiator, so it's
possible to use the bus for sharing devices between hosts, provided
your software can manage it.

See also the newsgroup comp.periphs.scsi, especially for "How do I
hook up a Brand X diskdrive to my Atavachron 9000 PDA?" type
questions.

------------------------------
Subject: [6.1.1] Single ended vs differential
From: (Device) Interfaces

This distinction is at the eletrical signalling level. However,
single-ended is limited to total bus lengths of 6.0 meters, while
differential can go up to 25 meters (SCSI-II). Differential is
generally more robust to noise and cross-talk, but the bus drivers are
more expensive. In theory no difference in transfer speed or
capabilities, but in practice the added noise margin could mean higher
_reliable_ transfer rates on your system, especially if your bus is
long.

Most disk drives and most low-end products are available only with a
single-ended interface. A few devices are available with either as a
purchase option, and a few are switchable by the user.

The cables and connectors are the same for both, though the pinouts
are (naturally) somewhat different.

Plugging a single-ended device into a running differential bus or
vice-versa may result in damage to one or more devices. Most newer
devices have fuses or protection circuits utilitizing the DIFFSENSE
signal to prevent device damage.

There are now recommended icons used to distinguish between the two:


single-ended                    differential
  /\                             //\
 /  \                           //  \
<   --                         <<   --
 \  /                           \\  /
  \/                             \\/


Converters do exist that will allow you to hook up single-ended
devices to a differential bus and vice-versa. People who have used
them say they work great, but in theory they shouldn't work :-).  As I
understand it, changing the signalling introduces delays in some of
the control signals that means that some devices could miss certain
signal transitions. The best advice is to borrow one and try it, and
see if it works in your system. One company's name is Parallan, I
think.

------------------------------
Subject: [6.1.2] Asynchronous vs Synchronous Transfers
From: (Device) Interfaces

Asynchronous transfers mean that every single byte must be
acknowledged before the next can be transfered. Synchronous means that
the device sending data can drop a series of transfers onto the bus,
toggling REQ or ACK (as appropriate), and then sit back and wait for
the corresponding pulses to return from the other device.

Async transfers, involving much more waiting, are correspondingly
slower. 2-4 MB/sec are good values for async transfers.

Sync transfer speeds are established during a negotiation between the
initiator and target, but devices are not required to use the full
speed they negotiate for. This speed represents the maximum burst rate
your device will use. Common values are 5 and 10 MB/sec.

In practice, virtually every modern device supports synchronous
transfers, but some implementations are better than others.

------------------------------
Subject: [6.1.3] SCSI-I vs SCSI-II vs SCSI-III
From: (Device) Interfaces

SCSI (now commonly known as SCSI-I) was the original 1986 standard,
X3.131-1986.  It specified the electrical level and some of the
mid-layer issues involving messages and packet structure, but (I
believe, my memory's bad) didn't formalize the Common Command Set
(CCS), that was done independently. It supported a maximum burst rate
of 5 MB/sec. on an 8-bit bus.

ADDITIONAL INFORMATION
     Consult the SCSI standards documents, and the manuals for the device you
     are working with for more information.  The "SCSI 1" specification
     document is called SCSI Specification, ANSI X3T9.2/86-109. Also of
     interest is the Common Command Set specification document SCSI CCS
     Specification, ANSI X3T9.2/85-3

SCSI-II received final approval in early 1994, but has been a de facto
standard for several years. The CCS was standardized for a variety of
different types of peripherals. The max allowable transfer rate was
raised to 10 MT/s (see below). A 16-bit bus (Wide SCSI) and 32-bit bus
(double-wide SCSI) are specified (see below).

SCSI-III is the latest effort, and involves more cleanly separating
the functionality into layers; the command layer is defined
independently from the physical layer. In addition to the traditional
parallel cable, there are efforts going on to define physical layers
for Fibre Channel and a more generic Serial SCSI. Thus, there will be
no SCSI-IV; only the individual pieces will be updated as necessary.

------------------------------
Subject: [6.1.4] Fast-Wide SCSI
From: (Device) Interfaces

The max allowable transfer rate was raised to 10 MT/s (mega-transfers
per second) in SCSI-2, referred to as Fast SCSI. Note that this is NOT
required, devices running at ANY speed below that may claim to be
SCSI-II compliant! Fast implies SCSI-II, not the other way around!
Fast Narrow is thus 10 MB/sec. Both the initiator (computer) and
target (peripheral) must support fast transfer for it to be of any
use, but intermixing fast and slow devices on a bus presents no
operational problems (only performance ones).

A 16-bit bus (Wide SCSI) and 32-bit bus (double-wide SCSI) are
specified in SCSI-2. The wide busses require the use of a second cable
in SCSI-2. The first cable is 50 pins, known as the A cable; the 2nd
is 68 pins, known as the B cable. I know of no one actually using
32-bit SCSI, but it would also run on an A/B cable pair. Slow (or
Normal) Wide is thus 5 MT/s * 2 Bytes/T, 10 MB/sec. Fast Wide is 20
MB/sec. Fast Double Wide would be 40 MB/sec.

In the SCSI-3 physical layer spec (SCSI-PH), a single 68-pin cable,
known as the P cable, is allowable for 8 or 16-bit busses. This is the
option most people who have implemented Wide SCSI have chosen for the
cabling, even though their upper layer is generally SCSI-2.

There is a small movement (heard here on the net occassionally) to
promote an Ultra-SCSI high-speed bus, with a burst rate of something
like 20 MT/sec on very short cables. At present it is unclear what
will happen to this effort.

------------------------------
Subject: [6.1.5] Shared Busses / Performance {Brief}
From: (Device) Interfaces

Also known as, "It's only a 500KB/sec. tape drive, why do I care if
the burst rate is only 2 MB/sec.?" or gets good marks for "plays well
with others".

Most of this is relevant to all shared busses, not just SCSI.
burst v. sustained performance, disconnect, command overhead, etc.

------------------------------
Subject: [6.1.6] Cabling/Hot Plugging {Brief}
From: (Device) Interfaces

Nominally not supported.

------------------------------
Subject: [6.1.7] Third Party Transfers/Separation of Control & Data Paths {Brief}
From: (Device) Interfaces

SCSI-2 has commands that support third-party copying of data; one
initiator tells device A to copy to device B. I don't know of any
devices actually using this.

Separation of control & data paths is a popular topic these days; can
somebody comment on whether or not SCSI-3 supports this? I don't think
so. (SHMO)

------------------------------
Subject: [6.2] IDE {Brief}
From: (Device) Interfaces
        PC use
        Does not support overlapped I/O.

------------------------------
Subject: [6.3] IPI {None}
From: (Device) Interfaces

------------------------------
Subject: [6.4] HIPPI {Brief}
From: (Device) Interfaces

32-bit transfers at 25 MT/sec., 100 MB/sec. High Performance Parallel
Interface is a unidirectional channel, i.e. you have to have an OUT
cable and and IN cable for bidirectional transfers (you could have
just one, if it's a read-only device like a scanner or write-only like
a frame buffer). HiPPI is not a shared bus, but its frames can be
switched through a crossbar switch (Network Systems is the premiere
vendor).

HiPPI is used for supercomputer-to-supercomputer networking (TCP/IP,
no less), for RAID arrays (from Maximum Strategy, IBM and others),
tape drives (Sony ID-1 drive), frame buffers and increasingly
workstations (SGI and IBM support HiPPI, and 3rd-party Sbus cards
exist for Sun).

Due partly to the high overhead of HiPPI connections, many devices
have elected to separate the control path from the data path. A common
control path in that case is ethernet.

------------------------------
Subject: [6.5] Ultranet {Brief}
From: (Device) Interfaces

Fiber to the host, a hub with a backplane running at a total rate of
~1Gbps.

------------------------------
Subject: [6.6] Ethernet {Brief}
From: (Device) Interfaces

Generally related to normal inter-machine networking, but also used as
a control path for some HiPPI devices.

------------------------------
Subject: [6.7] FDDI {None}
From: (Device) Interfaces

------------------------------
Subject: [6.8] Fibre Channel Standard (FCS) {None}
From: (Device) Interfaces

------------------------------
Subject: [6.9] ESCONN {Brief}
From: (Device) Interfaces

Enterprise Systems CONNect. IBM's new mainframe attach -- fibre, I
believe.

------------------------------
Subject: [6.10] Serial Bus {None}
From: (Device) Interfaces

------------------------------
Subject: [6.11] Multibus, Unibus, Mainframe Channels, and other history {None}
From: (Device) Interfaces

------------------------------
Subject: [7] Other
From: Other
------------------------------
Subject: [7.1] Video vs Datagrade tapes {brief, 5/94}
From: Other
        cost vs reliability
        Are datagrade really more reliable?
        Warrantee of drive
        Cleaning cycle of drive
        Headlife of drive


------------------------------
Subject: [7.2] Compression {New}
From: Other

See the comp.compression FAQ, and don't believe everything a vendor
tells you. 2x compression is the standard going rate for lossless
compression of arbitrary data, though some vendors claim 2.5 or 3x.
Your mileage will vary with your data type.

Compressing tape drives are common, but for disks and other block
devices I don't know of anything being done. The unpredictability of
the compression ratio generally makes it inappropriate for devices
that need fixed capacities and addresses.

Online compression of files can be accomplished by hand using
utilities such as gzip and Unix compress. Some systems support
software compression of files in the file system software, and will
transparently compress and decompress files as needed. Stacker for PCs
is one example; for Unix-like systems this seems to be common research
for object-oriented file systems (including the GNU Hurd), but I don't
know of any production versions offhand (SHMO).

Compression may make your data more vulnerable to errors. A single
error early in a compressed stream of data can render the entire data
stream unreadable.

------------------------------
Subject: [8] Benchmarking {New}
From: Benchmarking {New}

See the comp.benchmarks FAQ, and don't believe everything a vendor
tells you.

Bonnie, IOZONE, IOBENCH, nhfsstone, one of the SPECs (SFS), are all
useful for measuring I/O performance. There is also a program called
BENCHMARK available from [e-mail] -- apparently a
standardized set of scripts to test remote access to mass storage
systems.

 ==== SPEC SFS {New} ====

SPEC's System-level File Server (SFS) workload measures NFS server
performance. It uses one server and two or more "load generator"
clients.

SPEC-SFS is not free; it costs US$1,200 from the SPEC corporation.
There's a FAQ about SPEC posted sometimes in comp.benchmark.

------------------------------
Subject: [9] Mass Storage Conferences
From: Mass Storage Conferences

There are two main academic conferences devoted specifically to mass
storage (in addition to, of course, the supercomputer and OS
conferences, and interesting stuff in databases, optical
conferences...).

NASA and the IEEE run two conferences, in an 18-month or so
alternating pattern.

The contact for the NASA Mass Storage Conference (upcoming March
28-31, '95):


Jorge Scientific Corporation
7500 Greenway Center Drive
Suite 1130
Greenbelt, MD USA 20770
tel[phone]
fax[phone]


or if that fails email [e-mail]

Also, the next IEEE is in September:

* The 14th IEEE Mass Storage Symposium is September 11-14, 1995 at
  Monterey, CA.  More info from Bernie O'Lear ([e-mail]) or
  Sam Coleman ([e-mail]).

------------------------------
Subject: [10] MTBF (Mean Time Between Flareups, er, Failures)
From: MTBF (Mean Time Between Flareups, er, Failures)

This topic appears here on a regular basis, usually wrt disk drives,
and we always start with something naive, get a few things right and a
few more wrong before it dies down. It's perhaps the topic that
generates the most heat in this newsgroup. Somebody want to write this
section for me? (SHMO)

The one thing we seem to be able to agree on is that an MTBF of 57
years does _not_ mean that keeping your hard disk for 57 years is a
good idea!

There is a _great_ deal of disagreement here about this topic. If
somebody will write a good, non-inflammatory section for this,
including both theoretical references and maybe equations, and citing
examples on how to interpret the numbers manufacturers give, I will
include it here.

------------------------------
Subject: [11] Mass Storage Reports
From: Mass Storage Reports

There are a number of consultants who also write regularly updated
in-depth reports (and sometimes post here) about various aspects of
the mass storage market; if you're going to get into this business or
are planning on spending many thousands or millions of dollars on
equipment, talking to one of them might be a good idea.

Sanjay Ranade ([e-mail]) is one of the ones who both writes
and posts here (he also has a couple of reasonably-priced books about
mass storage).

Others include Disk/Trend (Mountain View, CA, but I've misplaced their
phone number) and Freeman Reports (805-963-3853).

------------------------------
Subject: [12] Appendix
From: Appendix

------------------------------
Subject: [12.1] Other References
From: Appendix

        Computer Technology Review magazine, 310/208-1335, free to some.
        Electronic News, weekly, 800/722-2346.
        MacWeek, June 7, 1993, Page 36+
    IEEE Computer had a full issue recently (early '94) on I/O systems

There are also two books by Sanjay Ranade ([e-mail]), who
posts here occassionally. One is _Mass Storage Technologies_, the
other, newer one is _Mass Storage Systems_. I've read the first one,
it's a little short on detail but a good overview.

------------------------------
Subject: [12.2] Epoch vs Unitree
From: Appendix
        (6/93) We just bought both last year.  We bought an Epoch I
with the 20 GB EO and 327 GB worm.  We will be upgrading it to an
Epoch II soon.  We also bought Unitree from Titan to run on a Silicon
Graphics server and hook up to the STK 3480 silo.  We hope to add more
silos eventually.

Unitree is licensed based on storage capacity while Epoch is not.
There may be an exception to this - STK just began reselling Epoch as
the front end for their silos and I'm not sure how they handle
licensing.

My office mate and I (I handle Epoch, he handles Unitree) have enjoyed
comparing the merits/demerits of each over the last year.  Comparison
in our case is slightly slanted due to the fact that the Epoch has
optical disk while the Unitree system has 3480 tape - so some
observations have more to do with media advantages/disadvantages.


        Unitree

+  Allows large files - can span volumes
+  Allows you to enlarge the cache easily, allows very large
cache
+- Unitree has replaced several UNIX utilities with their own
(FTP, NFS and the file system).  This allows certain features to
work but is generally slower and disallows access to the archive when
you are on the server itself - unless you NFS mount!
+  Allows deleted files to be saved for a specified time
+  Allows multiple copies of files to be kept
+  Data is copied to archive soon after creation
+  Unitree runs on several different platforms
-  Does not allow access to data until it is completely
reloaded
-  Behaves poorly with small files (due to necessary overhead)
-  Unitree is licensed to several vendors, so versions differ
-  NFS access is so slow that we recommend it not be used for
file transfer - only for ls and du, etc.  Use FTP.
-  The Silicon Graphics version is still new and has some
problems

        Epoch

+  Allows access to the data as soon as part of it is loaded
+  Company seems serious about reputation and support
+  The Epoch II is based on a SUN system, with few
modifications
+  Data is copied to archive only when the cache space is
needed
+  All native UNIX transfer methods work - NFS, FTP and RCP
+  Add on products greatly simplify backup and extend
archiving features to other systems.
-  Deleted files are gone forever
-  Currently only available on SUN.  This will change.
-  Cannot span volumes yet - limiting file size
-  Has the SUN limitation of 2 Gb per filesystem.  This would
be a bigger problem if you used it for a 3480 silo.
{Note 2GB of Magnetic Disk limit, not the entire HSM store}
-  Behaves poorly with small files (due to necessary overhead)
-  Since inodes are kept on magnetic cache, you must take
into account the maximum number of files you will ever need.
-  Since inodes are always on disk, certain disk operations
can take forever since all inodes must be examined.
-  Enlarging a magnetic disk filesystem which has associated
archive media requires you to offload all data and then reload it.
If anyone has found another way, I would like to hear about
it.
                   {Others did offer some easier work-arounds}


In all fairness to Titan, they have been addressing any problems and
it has been improving.  Epoch too plans to address some of their
shortcomings.  We are looking forward to growing with both products.

The likelihood that the various flavors of Unitree will standardize
depends on what happens with Discos.  My guess is that some
features/enhancements will be filtered back to the base product
released by Discos.  Bye...

        ([e-mail], 152.61.192.66, Tom Bodoh, USGS/EROS Data
Center, Sioux Falls, SD)

------------------------------
Subject: [13] ORIGINAL CALL FOR VOTES
From: ORIGINAL CALL FOR VOTES

NAME:
          comp.arch.storage

STATUS:
          unmoderated


DESCRIPTION:

        storage system issues, both software and hardware


CHARTER:

To facilitate and encourage communication among people interested in computer
storage systems.  The scope of the discussions would include issues relevant
to all types of computer storage systems, both hardware and software.  The
general emphasis here is on open storage systems as opposed to platform
specific products or proprietary hardware from a particular vendor.  Such
vendor specific discussions might belong in comp.sys.xxx or comp.periphs.
Many of these questions are at the research, architectural, and design levels
today, but as more general storage system products enter the market,
discussions may expand into "how to use" type questions.


RATIONALE:

As processors become faster and faster, a major bottleneck in computing
becomes access to storage services:  the hardware - disk, tape, optical,
solid-state disk, robots, etc., and the software - uniform and convenient
access to storage hardware.  A far too true comment is that "A supercomputer
is a machine that converts a compute-bound problem into an I/O-bound
problem."  As supercomputer performance reaches desktops, we all experience
the problems of:

o       hot processor chips strapped onto anemic I/O
                architectures
o       incompatable storage systems that require expensive
                systems integration gurus to integrate and
                maintain
o       databases that are intimately bound into the quirks of an
                operating system for performance
o       applications that are unable to obtain guarantees on when
                their data and/or metadata is on stable storage
o       cheap tape libraries and robots that are under-utilized
                because software for migration and caching to
                disk is not readily available
o       nightmares in writing portable applications that attempt
                to access tape volumes

This group will be a forum for discussions on storage topics including the
following:

>1.     commercial products - OSF Distributed File System (DFS)
        based on Andrew, Epoch Infinite Storage Manager and
        Renaissance, Auspex NS5000 NFS server, Legato
        PrestoServer, AT&T Veritas, OSF Logical Volume Manager,
        DISCOS UniTree, etc.
>2.     storage strategies from major vendors - IBM System
        Managed Storage, HP Distributed Information Storage
        Architecture and StoragePlus, DEC Digital Storage
        Architecture (DSA), Distributed Heterogeneous Storage
        Management (DHSM), Hierarchical Storage Controllers, and
        Mass Storage Control Protocol (MSCP)
>3.     IEEE 1244 Storage Systems Standards Working Group
>4.     ANSI X3B11.1 and Rock Ridge WORM file system standards
        groups
>5.     emerging standard high-speed (100 MB/sec and up)
        interconnects to storage systems: HIPPI, Fiber Channel
        Standard, etc.
>6.     POSIX supercomputing and batch committees' work on
        storage volumes and tape mounts
>7.     magnetic tape semantics ("Unix tape support is an
        oxymoron.")
>8.     physical volume management - volume naming, mount
        semantics, enterprise-wide tracking of cartridges, etc.
>9.     models for tape robots and optical jukeboxes - SCSI-2,
        etc.
>10.    designs for direct network-attached storage (storage as
        black box)
>11.    backup and archiving strategies
>12.    raw storage services (i.e., raw byte strings) vs.
        management of
        structured data types (e.g. directories, database
        records,...)
>13.    storage services for efficient database support
>14.    storage server interfaces, e.g., OSF/1 Logical Volume
        Manager
>15.    object server and browser technology, e.g. Berkeley's
        Sequoia 2000
>16.    separation of control and data paths for high performance
        by removing the control processor from the data path;
        this eliminates the requirements for expensive I/O
        capable (i.e., mainframe) control processors
>17.    operating system-independent file system design
>18.    SCSI-3 proposal for a flat file system built into the
        disk drive
>19.    client applications which bypass/ignore file systems:
        virtual memory, databases, mail, hypertext, etc.
>20.    layered access to storage services - How low level do we
        want device control?  How to support sophisticated, high
        performance applications that need to bypass the file
        abstraction?
>21.    migration and caching of storage objects in a distributed
        hierarchy of media types
>22.    management of replicated storage objects
        (differences/similarities to migration?)
>23.    optimization of placement of storage objects vs. location
        transparency and independence
>24.    granularity of replication - file system, file, segment,
        record, etc.,
>25.    storage systems management - What information does an
        administrator need to manage a large, distributed storage
        system?
>26.    security issues - Who do you trust when your storage is
        directly networked?
>27.    RAID array architectures, including RADD (Redundant
        Arrays of Distributed Disks) and Berkeley RAID-II HIPPI
        systems
>28.    architectures and problems for tape arrays - striped tape
        systems
>29.    stable storage algorithm of Lampson and Sturgis for
        critical metadata
>30.    How can cheap MIPS and RAM help storage? -  HP DataMesh,
        write-only disk caches, non-volatile caches, etc.
>31.    support for multi-media or integrated digital continuous
        media (audio, video, other realtime data streams)

This group will serve as a forum for the discussion of issues which do not
easily fit into the more tightly focused discussions in various existing
newsgroups.  The issues are much broader than Unix (comp.1.*, comp.os.*),
as they transcend operating systems in general.  Distributed computer systems
of the future will offer standard network storage services; what operating
system(s) they use (if any) will be irrelevant to their clients.  The
peripheral groups (comp.periphs, comp.periphs.scsi) are too hardware oriented
for these topics.  Several of these topics involve active standards groups
but several storage system issues are research topics in distributed systems.
In general, the standards newsgroups (comp.std.xxx) are too narrowly focused
for these discussions.


--------------------------------------------------------
------------------------------
Subject: [14] Original Author's Disclaimer and Affiliation:
From: Original Author's Disclaimer and Affiliation:

This information is believed to be reasonably accurate although I do
not verify every submission.  Neither the United Stages Government nor any
agency thereof, nor any of their employees, makes any warranty, express or
implied, or assumes any legal liability or responsibility for the accuracy,
completeness, or usefullness of any informatin, apparatus, product, or
process disclosed, or represents that its use would not infringe privately
owned rights.  Reference herein to any specific commercial product, process,
or service by trade name, trademark, manufacturer, or otherwise, does not
necessarily constitute or imply its endorsement, recommendatin, or favoring
by the United States Government or any agency thereof.  The views and
opinions of authors expressed herein do not necessarily state or reflect
those of the United States Government or any agency thereof.


---
Joseph Stith, [e-mail], 708/840-3846
Assistant to the Computing Division Head -- IRM Planning
Computing Division, Fermilab, PO Box 500, MS 120, Batavia, IL 60510


------------------------------
Subject: [15] Copyright Notice
From: Copyright Notice

This compilation of material is copyright Rod Van Meter,
[e-mail]. Permission is granted to copy this material,
provided this copyright notice is retained. The contents are not to be
significantly modified without the express written consent of the
author.

This is just to keep the various authors of this material from being
substantially misquoted or abused, not to restrict use of the
information.

------------------------------
Subject: [16] Additional Topics to be added
From: Additional Topics to be added

File Systems: Unix, IBM, VMS, Tops-20, Extent-based, Amiga, Mac
(resource & data forks)
FTP Sites
Volume Sets & Partitions
Important People/Mass Storage History
Books & Other Publications
Principles for Evaluating New Technologies
Performance Evaluation
  cacheing
  seek time measurement
  concurrent operations
  queueing theory
Head Lifetime
Versioning in File Systems
Managing Risk
Media Migration/Managing Change
Physical v. Logical Addressing (seek optimizations, etc.)
Channels v. Busses
Intelligent Storage Subsystems
DEC's HSC-50 and star cluster for VAXen
Mainframe & Supercomputer I/O controllers
Security
The broadcast and home audio/video / mass storage connection
Databases and Mass Storage
File System Research: watchdogs, named pipes, compressing FSes
The naming problem: Prospero
Distributed Locking & Update
Content-Addressable Storage & Other Unusual Ideas
The old film-storage system Sam Coleman talks about
Byte Ordering
Supercomputer Storage
Companies: Adstor, Avastor
I/O Benchmarks
User file systems
System CPU & bus loads for file system work
Memory-Mapped Files
Persistent Object Systems & their files
The VFS layer in Unix
What to look for in a backup product
Offsite Storage v. Network Backup
Test Equipment -- SCSI & HiPPI Analyzers
(reorganize along small user/large user/developer lines?)
(need to date every entry if possible)
terminology