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Q138310: Microsoft Plus! Drvspace.txt File Contents

Article: Q138310
Product(s): Microsoft Windows 95.x Retail Product
Version(s): 95
Operating System(s): 
Keyword(s): win95
Last Modified: 03-JUN-1999

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Plus! for Windows 95 
-------------------------------------------------------------------------------

SUMMARY
=======

The following information is a copy of the information in the Microsoft Plus!
for Windows 95 Drvspace.txt file.

MORE INFORMATION
================

--------
CONTENTS
--------

USING COPY-PROTECTED SOFTWARE WITH DRIVESPACE 3
FREEING CONVENTIONAL MEMORY FOR RUNNING MS-DOS PROGRAMS
USING DISK TOOLS WITH SIDEKICK FOR WINDOWS
COMPRESSION AGENT AND THE WINDOWS SWAP FILE
AUTOMOUNTING COMPRESSED FLOPPY DISKS
FREQUENTLY-ASKED QUESTIONS

COMPRESSING AND UPGRADING DRIVES
================================

Using Copy-Protected Software With DriveSpace 3
-----------------------------------------------

If you use copy-protected software, contact the manufacturer
before you compress or upgrade your drive using DriveSpace 3.
Some copy-protected software depends on the absolute physical
location of a "key" file, and will not work properly with
DriveSpace 3.

You might be able to work around this problem by uninstalling
the copy-protected software and then reinstalling it after
compressing or upgrading your drive.

If a Drive Becomes Inaccessible After You Compress Another Drive
----------------------------------------------------------------

If, after compressing a drive, your CD-ROM drive or another hard
disk drive becomes inaccessible or "disappears", the drive letter
may have been changed when DriveSpace reserved drive letters for
other purposes.

To restore the original drive letter:

1. Use the right mouse button to click the My Computer icon on
  the desktop, and then click Properties.

2. Click the Device Manager tab.

3. Click the + sign to the left of the Disk Drives item, click
  the drive you want to restore, and then click Properties.

4. Set the drive letter back to the original drive letter for
  that drive.

If the original drive letter is not available, it is probably
in use by the host drive. (You can change the host drive to
use a different letter. To do this, run DriveSpace, select
the host drive, and choose Change Drive Letter from the
Advanced menu.)

FREEING CONVENTIONAL MEMORY FOR RUNNING MS-DOS PROGRAMS
=======================================================

Some MS-DOS-based programs (for example, networks or games) may
not be able to run if DriveSpace 3 compression is installed, even
if you have not yet upgraded your drives to DriveSpace 3 format.
Typically, this problem occurs only when Windows is not running,
and with programs that require a lot of conventional memory.

To get your program to run, you need to reconfigure your
system so that more conventional memory is available.

The general steps involved are:

1. Make sure your CONFIG.SYS file contains commands like the
  following:

       DEVICE=C:\WINDOWS\HIMEM.SYS
       DEVICE=C:\WINDOWS\EMM386.EXE NOEMS
       DOS=HIGH,UMB
       DEVICEHIGH=C:\WINDOWS\COMMAND\DRVSPACE.SYS /MOVE

  These commands make it possible for DriveSpace to use
  upper memory, which can free more conventional memory for
  your program.

  NOTE: If the DEVICEHIGH command for DRVSPACE.SYS contains
        the /L:0 switch, delete the /L:0 from that command.

  If your CONFIG.SYS file does not contain these commands,
  add them. (To check whether DriveSpace is using upper
  memory, type MEM /C at the MS-DOS prompt.)

2. Restart your system, and then try running your program again.

3. If your program still does not run, disable any unnecessary
  drivers and memory-resident programs in your AUTOEXEC.BAT
  and CONFIG.SYS files.

  Try loading device drivers by using the DEVICEHIGH command
  instead of the Device command. For example:

       DEVICEHIGH=C:\WINDOWS\IFSHLP.SYS

  Try loading memory-resident programs by using the LOADHIGH
  command. For example:

       LOADHIGH DOSKEY

  Restart your computer, and then try running your program again.

4. If your program still does not run, you need to create
  a startup floppy disk that you can use to start your computer
  without DriveSpace. You can then run your program from your
  uncompressed (host) drive. For more information, see the
  following section.

Creating a Startup Disk for Running MS-DOS Programs
---------------------------------------------------

If your MS-DOS program does not run because there is not enough free
conventional memory, and you have carried out the procedure in the
previous section, you may need to create a special startup floppy
disk. You can then use that disk to start your computer without
DriveSpace, and then run your program from your uncompressed drive.

To create your startup disk, you will need the Startup Disk wizard,
Nocomp.Exe, which is located in the System subfolder of the folder
that contains your Microsoft Plus! files.

1. Make sure there is enough free space on your host drive (or
  another uncompressed drive) to install your program.

  To create more free space on your host drive, use the Adjust
  Free Space command in DriveSpace. (For other ways to free space,
  look up "Disk space, freeing" in the Help index.)

2. Run the Startup Disk wizard to create your startup floppy disk.

  NOTE: You will need a formatted or unformatted floppy disk that
        fits in drive A.

3. After the Startup Disk wizard finishes creating your startup
  floppy disk, insert the disk in drive A, and then restart
  your computer.

  Your computer will start without loading DriveSpace. This will
  free memory for your program to use.

  NOTE:  Your compressed drives will be temporarily unavailable.
         They will become available again when you restart your
         computer normally.

4. Install your program on your host drive or on another
  uncompressed drive.

USING DISK TOOLS WITH SIDEKICK FOR WINDOWS
==========================================

If Sidekick for Windows version 2.0 is running, you may be unable to
run certain disk tools, such as DriveSpace or Disk Defragmenter.

To work around this problem, first exit Sidekick, and then try
running the disk tool again.

For an update to Sidekick that fixes this problem, contact the
manufacturer.

COMPRESSION AGENT AND THE WINDOWS SWAP FILE
===========================================

When Compression Agent recompresses the files on your compressed
drive, it automatically skips the Win386.swp file. (This file,
known as the Windows swap file, provides virtual memory for
Windows and applications to use.) There is no need to specifically
exclude the Win386.swp file from compression by using Compression
Agent's Exceptions dialog box.

AUTOMOUNTING COMPRESSED FLOPPY DISKS
====================================

DriveSpace 3 automatically mounts compressed floppy disks and
other removable media when Windows 95 is running.

However, when Windows is not running (for example, if you restart
your computer in MS-DOS mode), automounting is disabled. To
mount a compressed floppy disk yourself, you can use ScanDisk.
For example, to mount the compressed floppy disk in drive A,
type the following at the command prompt:

   C:\> SCANDISK /MOUNT A:

FREQUENTLY-ASKED QUESTIONS
==========================

This section answers some common questions about how Windows
and DriveSpace report space usage on DriveSpace 3 drives.

Why do my files seem to take up more space on a DriveSpace 3 drive?
-------------------------------------------------------------------

The space on each drive is divided into units called clusters.
Each file or folder is stored in one or more clusters. When
Windows stores a file on your drive, it allocates just enough
clusters to hold the entire file. Because all the clusters on
a particular drive are the same size, a portion of the last
cluster for each file will probably be unused. For example,
on a drive that uses 8K clusters, each file uses at least
one 8K cluster, even if that file is only 1K in size.

Windows keeps track of used space on a per-cluster basis:
when Windows reports how much space is used by a file, it
includes the unused space at the end of the file's last
cluster. For example, Windows would report that a 1K file
uses 8K of space.

Larger drives have larger cluster sizes. In order to support
very large (2GB) drives, DriveSpace 3 uses 32K clusters.
This means that even a very small file still uses 32K of
space. As a result, when you view the properties for your
drive, the amount of used space might appear to be higher
than before you compressed the drive with DriveSpace 3.

Does this mean that more space is wasted on DriveSpace 3 drives?
----------------------------------------------------------------

No. On the contrary, DriveSpace 3 stores files much more
efficiently than on an uncompressed drive. In addition
to saving space by compressing the data in each file,
DriveSpace 3 also saves space by allocating smaller amounts
of physical disk space for each file. Although Windows
still keeps track of files in units of clusters (which is
why your files may appear to take up more space), DriveSpace
actually uses 512-byte units when allocating physical space
for each file. This means that no more than 512 bytes of
actual disk space is wasted when allocating a file on a
DriveSpace 3 drive.

What is "reduced overhead"?
---------------------------

When you view the properties for a compressed drive and
click on the Compression tab, you'll typically see that some
disk space was saved due to "reduced overhead." This
is due to the fact that DriveSpace actually stores files in
512-byte increments, rather than in larger clusters, as
would happen on an uncompressed drive. Reduced overhead
reflects the amount of space saved by using this more
efficient allocation, relative to the amount of space that
would have been required to store the same files on the
same drive if it was uncompressed. Reduced overhead does
NOT include the savings from the actual compression of your
data.

What do the numbers on the Compression tab mean?
------------------------------------------------

The Compression tab of the property sheet for a drive
shows how your files are being compressed and how much
space each type of compression is saving.

For each type of compression, the compression ratio is
computed by dividing the amount of data stored in that type
of compression by the amount of physical disk space actually
used to store the data. For example, if you have 100MB of
data stored in UltraPack format, and its compression ratio
is 2.5 to 1, then DriveSpace 3 is storing that data using
only 40MB of physical space on your hard disk. As a result,
the Gain column indicates that you've saved 60MB of space by
using UltraPack compression.

The overall compression ratio for a drive is an average of
all the compression types, plus the savings from Reduced
Overhead. It represents the ratio between the amount of
space that would have been required to store the same files on
the same drive if it were not compressed, and the amount of
physical disk space that DriveSpace is actually using to store
those files.

Why isn't the compression ratio for UltraPack higher?
-----------------------------------------------------

UltraPack compression generally achieves the highest
possible compression. However, because DriveSpace can read
and write data stored in HiPack format more quickly than
data stored in UltraPack, it uses HiPack format unless
using UltraPack can save a significant amount of disk
space. Because only the data that is most difficult to
compress will be stored in UltraPack format, the ratio
shown for UltraPack may actually be lower than that for HiPack.

Why are some files not compressed at all?
-----------------------------------------

On many drives, a significant amount of data will be listed
as being uncompressed. There are several reasons that
particular files may not be compressed:

* Files that are smaller than 512 bytes are never
  compressed. (DriveSpace 3 compresses a file only
  if it can save at least 512 bytes of disk space by
  doing so.)

* Space used on your drive to store folders is never
  compressed.

* The Windows swap file is never compressed. (This file
  provides virtual memory by using space on your hard
  disk.)

* Certain files may not be compressed if you have
  configured Compression Agent to prevent it from
  compressing those files.

* Files that are already compressed, such as JPEG or ZIP
  files, typically can't be compressed any further by
  DriveSpace, so they are listed as uncompressed.

* Some files that do not compress well, such as program
  files (.EXE and .DLL files), may have portions that do
  not compress at all. These portions are listed as
  uncompressed.

Additional query words: lock locked

======================================================================
Keywords          : win95 
Technology        : kbGamesSearch kbPlusSearch kbPlus95
Version           : 95

=============================================================================

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