Category : Tutorials + Patches
Archive   : STAC0694.ZIP
Filename : 31406.TXT

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STACKER NOTE STACKER NOTE
COMPRESSING A RAM DISK
(Applies to Stacker 3.1 for Windows & DOS)
STAC FAX 31406 (09/07/93)
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BACKGROUND

This document offers several strategies for compressing a ram
disk using Stacker 3.1. The procedures involve modifying your
configuration files, CONFIG.SYS, STACKER.INI, and AUTOEXEC.BAT.
Once these modifications are in place, Stacker automatically
compresses the ram disk every time you start your computer. See
document 31407, "Troubleshooting Stacker Ram Disks," for more
information.

SOLUTION

Create the ram disk
Position the ram disk
Compress the ram disk
Mount the compressed ram disk

Create the ram disk

Stacker 3.1 compression works exclusively on DOS disks with 512-
byte sectors. Random Access Memory (RAM) cannot be compressed,
but a device-driven disk created from RAM is an ideal candidate
for compression. Stacker cannot create a ram disk, but it can
compress one.

RAMDRIVE.SYS is an example of a ram disk utility that comes with
MS-DOS. This is an example of a minimal CONFIG.SYS file that
creates a one-megabyte ram disk in extended memory using
RAMDRIVE.SYS:

device=c:\dos\himem.sys
device=c:\dos\emm386.exe
device=c:\dos\ramdrive.sys 1024 /e

Your CONFIG.SYS file will be substantially different from this
minimal example. Consult your ram disk utility's user guide for
instructions on how to create a ram disk.


Position the ram disk

When assigning drive letters, DOS processes physical hard disks
and partitions first starting with letter "C." Next, DOS assigns
letters to device-driven drives like ram drives and Stacker
drives in the order in which they are loaded in the CONFIG.SYS
and AUTOEXEC.BAT.

For example, if you add a ram disk device driver to your
CONFIG.SYS file BEFORE the STACHIGH.SYS driver, then DOS
processes the ram disk first and assigns it the next available
drive letter. Conversely, if you add the ram disk device driver
AFTER the STACHIGH.SYS driver, or if the ram disk is created in
the AUTOEXEC.BAT file, then DOS processes the Stacker drive
letters first.

1. Follow your ram disk utility's instructions for creating a
ram disk. If the instructions include adding commands to
the AUTOEXEC.BAT file, ensure that they appear before the
Stacker command:

C:\STACKER\CHECK /WP

2. Reboot.

3. Note the startup message produced by the ram disk utility.
It normally indicates the ram disk drive letter.

4. Verify the integrity of the ram disk by running CHKDSK X:,
where X is the ram disk drive letter.


Compress the ram disk

After you have successfully created and positioned your ram disk,
you are ready to make the necessary configuration changes to
compress it. Stacker provides two utilities for compressing ram
disks:

SCREATE.SYS
This utility compresses ram disks from the CONFIG.SYS file.
Some ram disk utilities create ram disks in the AUTOEXEC.BAT
file. If your utility does this, then you must use CREATE
instead.

CREATE
This utility compresses ram disks from the AUTOEXEC.BAT file
and must be used if your ram disk utility completes creation
of ram disks in the AUTOEXEC.BAT file.


Using SCREATE.SYS

This is the syntax for compressing a ram disk in the CONFIG.SYS
file:

device=c:\stacker\screate.sys X:

where X is the ram disk drive letter.

1. Use a text editor to insert this command into the CONFIG.SYS
file. It should be the next command following your ram disk
device driver.

2. Save the file, exit the text editor, and reboot your
computer.

3. Ensure that SCREATE produces the following message when you
reboot:

SCREATE - 3.10, (C) 1991-93 Stac Electronics, Carlsbad CA
X:\STACVOL.DSK created successfully.


Using CREATE

This is the syntax for compressing a ram disk in the AUTOEXEC.BAT
file:
c:\stacker\create X: /b

where X is the ram disk drive letter.

1. Use a text editor to insert this command into the
AUTOEXEC.BAT file. It should appear immediately before the
Stacker check command, and after any ram disk commands:

[ possible ram disk commands...]
REM THE CHECK LINE BELOW PROVIDES ADDITIONAL SAFETY...
REM PLEASE DO NOT REMOVE IT.
c:\stacker\create X: /b
C:\STACKER\CHECK /WP

2. Save the file, exit the text editor, and reboot your
computer.

3. Ensure that CREATE produces the following message when you
reboot:

Stacker drive created successfully.


Mount the compressed ram disk

After you have successfully compressed your ram disk, you are
ready to make the necessary configuration changes to
automatically mount it.

If you compressed the ram drive using SCREATE.SYS BEFORE the
STACHIGH.SYS driver, then complete procedure 1, Mounting in
STACKER.INI. Otherwise complete procedure 2, Mounting in
AUTOEXEC.BAT.

1. MOUNTING IN STACKER.INI

1. Follow the instructions on page 15 of the Stacker 3.1
supplement to edit the STACKER.INI file.

2. Add the following command:

X:\stacvol.dsk,rp

where X is the ram disk drive letter.

3. Press Ctrl-Z to save the file.

4. Reboot.


2. MOUNTING IN AUTOEXEC.BAT

1. Determine if a replaceable drive is available. From the DOS
command prompt, type:

stacker

If the last line of the Stacker drive map indicates:

No available replaceable drive(s).

then complete step 1-A. Otherwise skip to step 2.

1-A. Follow the instructions on page 15 of the Stacker 3.1
supplement to edit the STACKER.INI file. If it already
contains the switch:

/RP=n

then increase n by 1. Otherwise, add this switch to the
beginning of the file:

/RP=2

then press CTRL-Z to save the modification.

2. This is the syntax for mounting a ram disk in the
AUTOEXEC.BAT file:

c:\stacker\stacker X:

where X is the ram disk drive letter. Use a text editor
to insert this command into the AUTOEXEC.BAT file. It
should appear immediately before the Stacker check command:

[ possible ram disk commands...]
REM THE CHECK LINE BELOW PROVIDES ADDITIONAL SAFETY
REM PLEASE DO NOT REMOVE IT.
[ possible c:\stacker\create X: /b command...]
c:\stacker\stacker X:
C:\STACKER\CHECK /WP
.
.
.

3. Save the modified AUTOEXEC.BAT file.

4. Reboot.
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Copyright 1993, Stac Electronics