home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Shareware Supreme Volume 6 #1
/
swsii.zip
/
swsii
/
163
/
2266.ZIP
/
2266.HOT
Wrap
Text File
|
1991-03-19
|
5KB
|
108 lines
M2266SA DISK DRIVE.
An article recently appeared in the Digital News magazine, which
described the possible "loss of data" a User may experience, when
using a Fujitsu M2266SA disk Drive.
What should be realized is that any such loss of data is not due to
a problem with the drive itself, but is caused by an improper
configuration of the System Software, or, Host Adapter/Firmware
which cannot properly utilize the full available capacity of the
M2266SA drive.
A brief explanation of the technical issue will follow and then a
recommendation of what the User should do in order to obtain
maximum capacity and secure operation of the product.
Fujitsu disk drives are manufactured in strict compliance with the
ANSI specifications for the SCSI disk drive interface and command
sets.
When the system software has to write or read data to and from the
disk, commands are sent which specify the address on the drive
where the data is located.
Early SCSI Software and Host Adapters utilized what are called
"Group Zero" commands, which have an address field of twenty one
bits of binary data, which means that the highest address available
is just over "One Thousand and Seventy Three Megabytes". (1.073
Gigabytes.)
Until recently, this was more than adequate to handle the disk
drives generally available in the typical SCSI environment.
In the ever-increasing growth of disk capacity, Fujitsu has
delivered the M2266SA drive which has a capacity of over "One
Thousand and Seventy Nine Megabytes (1.079 Gigabytes.)
This is more than Five Megabytes greater than is addressable by the
"Group Zero" commands !
What is needed to fully address drive capacities above the 1.073
Gigabyte limit, are the "Group One" command sets, (as defined by
ANSI), which have "Thirty Two bits" in the address field and can
address over Two Thousand One Hundred and Ninety Nine (2199)
Gigabytes. (Hopefully this will last for a while).
A number of Fujitsu Customers ran into questions or difficulties
during the installation phase with the M2266SA, while some we heard
from, appeared to have successfully performed the installation, but
who later had data on cylinder zero overwritten, due to an address
"wrap-around".
It appears that there is some relatively unsophisticated software
in use, which is writing data at the very top addresses of the
drive, is then incrementing addresses on subsequent write commands
and does not check to see if the maximum addressable limit has been
reached for group zero commands (i.e. 1FFFFF Hex.) An overflow
occurs out of the address field, therefore the next effective
address sent to the drive is zero, thus overwriting the data which
is already written there.
There are software systems using group zero commands perfectly
normally, not encountering any such problem, because at
installation time, appropriate parameters are given to the system,
so that it will only use the address capability available to the
group zero commands. For example, we believe that there is no
problem on a SUN system, but there could be a problem with DEC and
APPLE.
Obviously a drive Vendor such as Fujitsu is not privy to the
internal characteristics of the many Software Systems and Host
Adapters available and in use in the world today.
WHAT TO DO BEFORE INSTALLATION.
1. Ascertain FOR CERTAIN, from the Software and Host Adapter
suppliers, if the revision level of software and firmware to be
used is incorporating the "Group ZERO" or, "Group ONE" SCSI
commands. If "Group ONE", then there is no problem, proceed
with normal installation.
2. If the Software/Firmware uses "Group ZERO" commands, then it
would be best to upgrade to that which uses "Group ONE", so
that the full capacity of the drive can be used.
2a. If this path is not possible, then it must be ensured that
during installation, the drive capacity is set to 1.073
Gigabytes or less.
3. If 2a. cannot be accomplished by software, then the drive
should be reformatted down to 1.073 Gigabytes. (i.e. 1FFFFF
Hex. logical blocks)
(Note. This requires a "Mode Select Command" followed by a
Format command and not all systems make this possible for the
User, therefore the drive would have to be reformatted by some
other external equipment. In this case the Dealer,
Distributor, or Drive Vendor should be contacted for
assistance.)
Please refer to the following TECH. TIPS which have been published
by Fujitsu, to give some assistance in the correct installation of
the M2266SA drive.
FABBS File number.
M2266S 001 SUN INSTALATION. M2266SUN.INT
M2266S 002 SYSTEM INSTALLATION. M2266INS.INT