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FAQ 11

11. Disk compression and you

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 size)

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)

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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.

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.

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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 re-installation on!

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).

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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.

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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.

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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.

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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.

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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.

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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:


and re-boot.

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.

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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:

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.

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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.

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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 machines.

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.

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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

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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 scans)

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 Utilities)

1. Compressing your whole hard drive

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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 re-installing Win95)

5. It's useless on '386 machines

4. It makes my computer unstable (use System Agent to schedule disk scans)

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 MS Plus

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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