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Subject: Win95 FAQ Part 11 of 14: Disk Compression
This article was archived around: Sun, 8 Nov 98 20:11:39
Posting-Frequency: Every two months
Subject: 11. Disk compression and you
* 11.1. Why should I bother? (Actually it's not as dumb as you
* 11.2. I heard that using disk compression is helpful on drives
> 1 GB. Is this true? (yes.)
+ 11.2.1. Does disk compression on > 1 GB drives work with
FAT32 as well?
* 11.3. How do I compress my whole hard drive? (Avoid if
* 11.4. How do I compress a part of my hard drive?
* 11.5. How do I compress floppy disks?
+ 11.5.1. Enabling "Auto-mount" for removable compressed
* 11.6. The DriveSpace driver takes 60 KB and I can't load it
high! How do I do it?
* 11.7. The DriveSpace 3 driver takes 100 KB and I can't load it
high! How do I do it?
* 11.8. How do I start my computer WITHOUT loading the
+ 11.8.1. Why you should run DOS programs in DOS sessions
+ 11.8.2. How do I load the Win95 DriveSpace driver, but
NOT load the DOS DriveSpace driver?
* 11.9. My computer is very, very, slow since I installed disk
compression. How can I speed it up?
+ 11.9.1. Basic DriveSpace 3 theory; regular, HiPack,
UltraPack, Compression Agent
+ 11.9.2. Why on slow computers, you should use "No
compression" and still use DriveSpace 3
* 11.10. Top ten mistakes using disk compression
* 11.11. Top ten mis-conceptions regarding DriveSpace 3
Subject: 11.1. Why should I bother? (Actually it's not as dumb as you might think)
With hard drives getting cheaper every day, you will believe (and I do
too) that disk compression is a waste of processor time, a waste of
system memory, and it makes the system unstable. But, here are some
good reasons to use disk compression:
On FAT file systems, it wastes far less disk space (Cluster sizes are
minimum 512 bytes regardless of the partition's 'reported' cluster
It reduces the amount of CPU time spent on the hard drive (It reads
less off hardware)
It makes good use of smaller hard drives
Win95's disk compression take NO conventional memory (At least, when
you run Win95 that is)
Subject: 11.2. I heard that using disk compression is helpful on drives > 1 GB. Is this true?
DriveSpace 3, in particular, is helpful for drives > 1 GB, if you set
compression to "none". This is because DriveSpace will use a smaller
physical cluster size.
FAT file systems have a 65 thousand cluster limit (64 K, or 65 536
clusters); this means as the drive gets bigger, the cluster size gets
bigger too. On a 1 GB hard drive, the cluster size is 32 KB! That's a
lot of disk space wasted if your file is much smaller than 32 KB!
DriveSpace (and Stacker, and what-have-you) use their own file system
and emulate FAT, and they can compress the unused space in a cluster.
DriveSpace 3, in particular, will use no more than 512 bytes per
simulated cluster, if your file is smaller than this.
You can observe this by running DEFRAG on a compressed drive in Win95;
after the initial Defrag pass, it will de-fragment a second time,
showing the relative sizes of each cluster. Tightly compressed
clusters will appear shorter.
* 11.2.1. Does disk compression on > 1 GB drives work with FAT32 as
Apparently not. MS describes FAT32 in KB article Q154997 and they
clearly state that disk compression does not work on it (Hey, Stac
Electronics: That's your cue! Get on it!) This probably has something
to do with FAT32 being almost completely different from original FAT
and VFAT; the root directory being a real FAT chain instead of a
couple of sectors, for example.
Subject: 11.3. How do I compress my whole hard drive?
I say Avoid If Possible. If you have to re-install Win95, you might
not be able to read the compressed drive to perform the
However, it can be done. You will have to have Disk Compression
installed in Win95; check Add/Remove Programs / Windows Setup / Disk
Tools. Then, right-click on your target hard drive and bring up its
properties. You should see a Compression tab which gives you two
options. Select the option to compress the whole hard drive.
This built in compression (Affectionately called "DriveSpace 2") will
re-boot your computer and run a compression process in a "miniature"
Windows 3.1 environment. This means you can't use your computer while
this happens. This does take a long time, so you should get it started
and let it run overnight. When completed, you will have two active
drive letters, or volumes; your original hard drive (Re-named to "H:"
or some such thing) and your new compressed hard drive (Renamed "C:"
to replace your original hard drive).
Subject: 11.4. How do I compress a part of my hard drive?
OK so you heeded my warning. Good. You have to install Disk
Compression if you didn't already do so. Before running DriveSpace,
de-fragment the hard drive you're placing the compressed volume on.
This will maximize the space the compressed volume can take.
Then, bring up properties of the target hard drive. In the Compression
tab, select the option to create a new compressed volume. This will
run DriveSpace, create the new .CVF file, and tell you to re-boot your
computer. Much quicker.
If you plan to use DriveSpace this way, you should do so right after
you complete your Win95 installation, and create a compressed volume
with all the remaining space. This will maximize the drive space that
gets compressed, and keep your Win95 installation uncompressed, ready
to re-install if necessary. Maybe leave about 100 MB uncompressed for
the Program Files folder, which always goes on your booting drive.
Subject: 11.5. How do I compress floppy disks?
Bring up properties for your floppy drive, and select the
"Compression" tab. You only have one compression option here; you
can't put a separate CVF on a floppy disk. The rest of it works like
compressing your whole hard drive.
It's best to do this with blank disks; otherwise you will waste time
compressing the files already on the floppy. Use this technique for
any other removable media; optical disks, SyQuest disks, whatever.
* 11.5.1. Enabling "Auto-mount" for removable compressed disks
Back in DOS 6.0, you had to manually mount compressed floppies, and
unmount them before ejecting them. Win95 will automatically mount
compressed floppies if you allow it to.
Run DriveSpace, then in Advanced/Settings, turn on the Auto-Mount
switch. This is normally turned on by default. The first time you
access the removable disk, if it sees a DRVSPACE.xxx file, it will use
that instead of the actual disk.
No, you can't copy .CAB files to compressed floppies; the files in a
CAB are already compressed.
Subject: 11.6. The DriveSpace driver takes 60 KB and I can't load it high! How do I do it?
In order for Win95 to actually start, Win95 DOS has to see any
compressed drives you might have installed Win95 on. There is a real
mode DriveSpace driver (and a real-mode DRVSPACE.INI settings file) in
the root of your boot drive, though they're hidden.
If you have an empty CONFIG.SYS file (which you should), when Win95
starts it will remove the real mode DRVSPACE.SYS driver and run the
protected mode driver in its place, freeing up the 60 KB.
If you insist on keeping a DOS configuration (Or if you specified a
special DOS config for any of your games), you can continue to use
to re-locate the real mode driver to upper memory.
Subject: 11.7. The DriveSpace 3 driver takes 100 KB and I can't load it high! How do I do it?
Ahh... monster driver! This thing is so big because it needs to have
compression routines for the three types of compression: UltraPack,
HiPack, and Standard.
If you have enough upper memory, make the DRVSPACE.SYS /MOVE entry in
CONFIG.SYS the very next DEVICE= right after EMM386. This will eat 100
KB of upper memory of course, and the rest of your real mode drivers
probably won't fit in upper memory afterwards.
Win95 will unload this monster driver from conventional memory when
you run Win95, provided you didn't try to load it high. Do yourself a
favor and run your DOS programs in DOS sessions.
Subject: 11.8. How do I start my computer WITHOUT loading the DriveSpace driver?
Edit MSDOS.SYS and add or edit these lines to the [options] section:
NOTE: If you do this, you can't access compressed drives from DOS of
course, but you also can't access them in Win95 either! This is an
important reason not to compreess your whole hard drive.
* 11.8.2. How do I load the Win95 DriveSpace driver, but NOT load
the DOS DriveSpace driver?
Actually, there IS a way NOT to load the DriveSpace driver in MS-DOS
Mode, AND use the compressed drive in Win95! You'll find this trick
useful if you run many programs in Single Mode DOS or make up
special DOS configurations for certain programs and games, as it saves
a good 60 KB to 100 KB of conventional memory, and still lets you use
the compressed drive under Win95 and in DOS sessions.
This is a bit tricky, so only do it if you know what you're doing, AND
you aren't picky about what drive letter the compressed drive takes,
AND you didn't install Win95 on the compressed drive, AND you don't
assign any network shares on the compressed drive (You'd have to
re-share them each time you re-boot if you did this.)
1. Put in the entries to MSDOS.SYS above
2. Run Policy Editor, Select File/Open Registry, and in Local
Computer/System/Run Services, add this entry:
Name: Manually mount DriveSpace Drive (Actually you can call this what you want)
Value: DRVSPACE.EXE /MOUNT=001 C:
3. Save changes to the Registry, and test by re-booting to "Command
Prompt Only" (Press F8 on "Starting Windows 95..."). Check that you
have lots of conventional memory free.
4. Type WIN to start Win95. Before any other programs load, you should
get some floppy access and a message stating that your compressed
drive has mounted.
5. Now you can re-boot normally, once you're sure everything works.
What this does, is prevent the real mode DriveSpace driver from
loading at all. Again, this means you can't access compressed drives
outside of Win95. It also mounts the compressed drive, using protected
mode drivers, before any other Win95 programs start (Run Services runs
its programs before anything else does). You will get an annoying
message on start up, but you had to pay the price somewhere for this
cool trickery, no?
* Syntax of DRVSPACE.EXE /MOUNT command:
DRVSPACE /MOUNT=xxx y: /NEW=z:
Where "xxx" is the number of the compressed volume (Find out by
showing all files and looking for a DRVSPACE.001 file; the 001 is the
number you put in the MOUNT= parameter). "y:" is the drive letter
where the compressed volume exists. "z:" is the drive letter you
assign the new compressed drive in the /NEW= parameter. NOTE: /NEW=
does not always pick the drive letter you want, especially if you have
network drives. It's best to leave out the /NEW= and just live with
the drive letter it comes up with. You can specify a range of drive
letters in the DRVSPACE.INI file, if you choose, to make the
assignment consistent. Once it settles on a drive letter it will
consistently use it, until you remove the compressed drive or
re-assign the drive letter.
Subject: 11.9. My computer is very, very, slow since I installed disk compression. How can I speed it up?
DriveSpace works best in Win95 if you have lots of RAM (16 MB), have
lots of extra computing power ('DX2-66es are quite adequate for this),
and some external SRAM for processor caching (256 KB is best). The CPU
has to work harder to interpret compressed data, but it has to wait
less time to actually get it. This is the trade-off.
To speed compressed drives up, install DriveSpace 3 (in MS Plus!), and
set compression to "none", or "none, unless it is xx% full, then use
Standard". You still get the benefits of reduced cluster sizes even
though you aren't compressing data. Later on, you can use Compression
Agent to compress the drive overnight, or any other time you aren't
using the computer.
If you use DriveSpace 3 on a '486 class computer, do not use HiPack as
the default file format. There's a reason MS didn't recommend that.
Maybe even set compression to "None" and use Compression Agent to
re-compress overnight, using HiPack then. HiPack takes less time to
read than to write. Also, when using Compression Agent, DO NOT USE
UltraPack! UltraPack is very, very, slow on '486 machines. I wouldn't
even recommend it for Pentium machines slower than 100 MHz.
If you're too cheap to buy MS Plus, simply make sure your swap file
isn't on the compressed drive, and it's set to a fixed size. Do this
from System Properties/Performance/Virtual Memory. Win95 doesn't
actually compress the swap file, but it does go through the DriveSpace
driver to access it. Move it to an uncompressed drive to remove that
extra layer of protocol.
Finally, make sure you have NO real mode disk drivers to handle
CD-ROMs, etc, that might be sitting on the hard drive adapters. The
Win95 disk driver can't load then, and it won't use the Win95
DriveSpace driver either.
* 11.9.1. Basic DriveSpace 3 advice; regular, HiPack, UltraPack,
DriveSpace 3 makes more drive space by compressing files tighter. It
does so using Compression Agent, which gets automatically scheduled in
System Agent when you install MS Plus.
Run DriveSpace 3, select the compressed drive, then select
Advanced/Settings. This selects how DriveSpace writes data to the
compressed drive on the fly. As MS recommends, don't use HiPack on
'486 class computers. I won't even use it on Pentium-75s. "Standard"
is best for all '486 machines or better, though a slow '486 can
benefit from the "None until..." setting. Use "None" on all '386 class
Now, DriveSpace 3 can uncompress data faster than it can compress it,
so it makes sense to try to re-compress the drive during idle moments,
like overnight. Compression Agent does this.
Either in System Agent, or in Accessories/System Tools, run
Compression Agent and hit its Settings button. For Pentiums faster
than 100 MHz, you could try UltraPack, but I doubt you'll get a whole
lot of extra disk space from it. All '486 systems can benefit by
completely turning off UltraPack and specifying HiPack for the rest of
the files (basically meaning "All of them".) Generally, reading back
HiPacked files is quick, so you can specify that for even '386 class
machines, but if you really can't handle the decrease in speed, use
"Store them uncompressed".
A re-compression run does take a LONG time, so do it overnight. Use
System Agent to schedule re-compression, say, once a month, and
schedule a thorough disk scan about an hour before Compression Agent
runs. A Defrag after Compression Agent wouldn't hurt, but schedule it
for a LONG TIME after Compression Agent.
* 11.9.2. Why on slow computers, you should use "No compression" and
still use DriveSpace 3
It handles bigger hard drives (compressed volumes larger than 512 MB)
It reduces wasted disk space (for files smaller than 512 bytes, it
only occupies 512 bytes, regardless of logical cluster size)
It won't eat CPU time if you turn compression off
Subject: 11.10. Top ten mistakes using disk compression
10. Running your DOS games outside of Win95 (Not enough memory)
9. Deleting the DRVSPACE.001 file (Fortunately, Win95 has a safety
mechanism for that!)
8. Deleting the DRVSPACE.BIN file
7. Using an old DOS compression program
6. Using a DOS driver for your IDE CD-ROM and DriveSpace (Get Win95
drivers for the IDE port and it'll find the CD-ROM)
5. Not using ScanDisk regularly (Use System Agent to do automatic disk
4. Setting your estimated compression ratio higher than your real one
(Then installing a big game...)
3. Using UltraPack on a '386 computer
2. Using Norton Disk Doctor for Win95 on DriveSpace 3 drives (ScanDisk
is more reliable... Symantec released two patch sets to fix Norton
1. Compressing your whole hard drive
Subject: 11.11. Top ten misconceptions regarding DriveSpace 3 from MS Plus
10. Norton Utilities for Win95 works on it (Sorry... it reported false
errors on mine!)
9. It's faster than "DriveSpace 2" (At least not at first...)
8. I need a Pentium-133 to use it (Just don't use UltraPack)
7. It eats more conventional memory (Actually, it eats NONE under
Win95, if set up properly)
6. I can compress my whole drive with it (Yeah... then try
5. It's useless on '386 machines
4. It makes my computer unstable (use System Agent to schedule disk
3. A virus can wipe out the system (A nasty virus could wipe out the
system, compressed or not)
2. MS deliberately crippled Win95's built-in DriveSpace to make us buy
1. It's the best compression program for Win95 (Actually, it's the
ONLY one... heh heh... Stac, you lose this round)
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