Alles Voor Internet / Tout Pour Internet/alles voor internet.iso/MacInternet™/Archive-tools/times-two-compressor.txt

Internet Message Format | 1992-12-07 | 8KB

Date: Sat, 5 Dec 1992 15:46:14 -0500
From: [e-mail] (Tony Huang)
Subject: [*] TimesTwo (and comparison with other auto compression programs)

There have been some discussions about TimesTwo in the last few days and
here's my impression of the product (I originally intended to comment on
the product earlier but a project deadline kept me from doing this):

First of all, for those of you not familiar with the product, TimesTwo is a
HD formatter which replaces the existing SCSI driver with a driver that
does compression and decompression as data are written and read from the
disk. Since it's operating at the driver level and nearly all programs talk
to the HD through the driver, everything gets "compressed", and
theorectically, this process should be totally transparent (not so with any
other types of compression programs) and there should be no compatibility
problem with those programs (provided the driver is bug-free, of course).

In reality, however, this's not entirely the case (all softwares have bugs
- bug-free softwares are just not humanly possible), although TimesTwo does
fulfill most of its promises. Once installed correctly, TimesTwo does work
totally transparently and is very compatible with all the programs and
INITs that I use (Last time I counted I have 60 or so INITs active on my
machine which's running System 7.0.1 with 32-bit addressing turned on).
TimesTwoed disks can be moved to another machine (without TimesTwo
installed).

TimesTwo is reasonably fast, as least as fast as (subjectively it's faster
than) AutoDoubler (AD). I've used all background compression programs
currently available (including AutoDoubler, More Disk Space (MDS) and
SpaceSaver) for extended periods of time. AD was my background compression
program of choice although it has its share of compatibility problems and
it sometimes unneccessarily decompresses files to disk, which takes time
(THINK Reference database file comes to mind). MDS is arguably the fastest
decompressor (and slowest compressor) but it has some awful bugs and
doesn't work well as a background compression program (its resource
compressor, similar feature also available in AD 2.0, works quite well with
many - but not all - programs). SpaceSaver is the slowest of all as a
background compression program, although it has some of the nicest
features, especially if you use StuffIt Deluxe (I still use it but with
Idle Time compression turned off).

The compression ratio achieved with TimesTwo compares favorably with the
other auto compression programs. Since TimesTwo compresses everything
including files in the System folder, one might expect a much higher
overall compression ratio if his/her System folder is large. Unfortunately,
this's not necessarily true. My System folder takes up approximately 50Mb
of disk space, but most of them are already in compressed form (including
System, Finder, PS Type 1 outline fonts, etc. TT fonts are more
compressible unless they've already been compressed by Suitcase or
MasterJuggler). On the other hand, if you have lots of compressible files
in your System folder, TimesTwo is the best program to compress them.
Though MDS and AD 2.0 has resource or internal compressor to compress INITs
(and cdev's, etc.), you can run into many problems with many INITs ( I
have!) since the compressor itself is an INIT (in the case of AD) or a
patch (in the form of a resource) to the System file (MDS). TimesTwo has no
such problem. As Murph Sewall pointed out (Info-mac Digest V10 #289),
compression ratios for different types of files are obviously different and
the name TimesTwo is misleading at best (so is the name AutoDoubler, BTW).

If you have read thus far, you might have gotten the impression that
TimesTwo is a wonderful program. It may be (depending on your system
configuration, see below), but it certainly has its share of problems (some
of them are not the fault of the programmers). First, since TimesTwo
compresses everything on disk, Virtual Memory (VM) swap file gets
compressed as well. This can severely deteriorate the performance of your
system (I don't use VM so it's not a problem with me). If you use VM, don't
install TimesTwo on the drive containing the VM swap file. Even if you
don't use VM, you still may not want to install TimesTwo on your startyp
disk because the small performance penalty (if you have a reasonably fast
CPU) you have to pay (slower to read resources from the System file or to
load fonts from a suitcase, for example). I don't install TimesTwo on my
startup disk for this reason and because my System folder is barely
compressible (as I mentioned earlier).

Second, TimesTwo not only cannot partition (hard partition) disks, but
installation of TimesTwo on a partitioned disk erases all its data. Worse
yet, some existing SCSI drivers fools TimesTwo installer into thinking the
disk is partitioned even though there's only a single partition (I have
this problem with my SyQuest cartridges). TimesTwo does let you back out
the installation process, however.

TimesTwo can cause problem if you use removable media (such as SyQuest)
with different SCSI drivers (e.g. some formatted with TimesTwo, some with
another utility). The solution here, as usual, is to use SCSIProbe
(Freeware - latest version 3.4 available from sumex and other archives) to
close the driver after ejecting the cartrige. The side effect of this is
that the next cartidge won't mount automatically even if you have an
auto-mounting INIT installed (In fact, you should remove the auto-mounting
INIT. Otherwise it would surely lead to a crash, at some point if not
immediately. Use SCSIProbe or its keyboard shortcut to mount the next
cardrige). TimeTwo doesn't come with an auto-mounting INIT (one is planned
for release in the near future according to Golden Triangle, the maker of
TimesTwo). To be fair, this problem is not unique with TimesTwo; the same
problem exists with cartridges formatted with different HD formatters
(whether or not one of them is TimesTwo).

Lastly, copying files from a TimesTwoed disk to another (or itself) is
SLOWER because TimesTwo works so transparently (a virtue, I think) that the
Finder has to decompress (as it reads from disk) and then recompresses the
files (as it writes to disk). This is not a bug in the usual sense but
Golden Triangle has promised a fix (by making it "less" virtuous, I guess)
in a future release.

Finally, I want to comment on the complaint by Tonio Loewald (Info-mac
Digest V10 #289) that the original floppy is apparently copy-protected. I
agree that copy protection is annoying (and generally speaking, we should
avoid all copy protected programs). In this case it's stupid. The manual
says that "In the event of a disk crash, you should always start up from
the TimesTwo program diskette first and run verify before using a disk
recovery program like Disk Fisrt Aid, Norton Utilities or MacTools."  What
do I do if the original diskette is damaged? The copy protection scheme in
this case is also useless. The license agreement clearly states that one
backup copy can be made and I strongly encourage every TimesTwo owner to
make a backup copy. Here's how. Use FastCopy (bundled with MacTools Deluxe
1.2, but not 2.0), making sure you UNcheck the "Copy used sectors only"
option and the "Format before writing" option is checked, to duplicate the
original TimesTwo diskette. Other faithful disk duplicators (such as the
freeware DiskCopy 4.2 from Apple, or the shareware program DiskDuplicator+)
may also work, but I haven't tested them.

Tony Huang
[e-mail]

P.S. Moderators: This file should be archived as timestwo.txt in
info-mac/report. I'll make additions and corrections as more facts are
known about TimesTwo.