Stacker uses data compression. Compressing a file makes it use less space by eliminating repetitive pieces of information. After compressing the drive by running Stacker on it, you use it exactly as you did before running Stacker. Data, however, is automatically compressed when written to the drive and automatically decompressed when read back from the drive.
The amount by which a disk drive can be compressed depends on the type of files stored on it. Word processor files usually compress to half their original size, for example, while spreadsheet files compress even more. Programs and command files tend to compress less because they do not contain very much repetitive data.
This chapter describes the Stacker program and how to use it.
Warning: Never use the Stacker program on a Windows 95 computer.
After starting SETUP, do the following:
Compressing the Entire Hard Disk Drive
Compressing the entire drive means that all existing data on the drive will be compressed. After the drive is compressed, there will be more free space.
2. When compression is finished, you see the size of the stacked disk and the amount of free space, before and after compression.
Creating a Compressed Drive From Free Space on a Hard Disk
Instead of compressing an entire hard disk drive, you can choose to use all the free space on the drive to create a new Stacker drive. You compress free space the same way you compress the entire drive; refer to ``Compressing the Entire Hard Disk Drive'' on page 12-4 for a description. The only differences are as follows:
Instead of using SETUP, you can quickly compress a blank diskette by using the CREATE command at the system prompt. Refer to the ``Command Reference'' chapter of DOSBook for information about the syntax and function of the CREATE command.
SETUP automatically detects the presence of DoubleSpace or SuperStor drives when you choose Disk Compression from the main menu. When prompted, choose whether or not to convert all DoubleSpace and SuperStor drives to Stacker drives.
After converting drives via SETUP, it is a good idea to make sure your data is as safe as possible by recompressing your data using DISKOPT. The DISKOPT program includes an option to perform a full optimization and ``restack'' of the drive. For information about running DISKOPT, refer to Chapter 11, ``Improving Disk Performance.''
Warning: Never use the DR-DOS CHKDSK utility on a
Windows 95 computer, even under DR-DOS. Use the Windows 95 CHKDSK
The Compression Process
When you are compressing existing data, the Stacker program works on an uncompressed disk drive as follows:
Accessing Compressed Drives (STACKER.BIN and STACKER.INI)
The operating system needs information about how to access a compressed drive once it has been created.
Mounting and Unmounting Compressed Drives
After the Stacker program is run on any of your disk drives, compressed drives are automatically mounted when you boot the system and available to use. You may, however, need to unmount a compressed disk to access the uncompressed drive. You will also need to unmount compressed diskettes before you can run the DOS DISKCOPY or FORMAT commands on them.
Checking Compressed Drives
The Stacker program includes a way of checking the current status of your compressed drives, checking the integrity of those drives, and displaying information about them such as the compression ratio.
Displaying Drive Status
You can use the STACKER command at the system prompt to display a report on the status of each drive. Refer to the ``Command Reference'' chapter of DOSBook for information about the syntax and function of the STACKER command.
Checking Drive Performance and Usage
To check Stacker drive integrity, use the CHKDSK command. CHKDSK
includes options that apply specifically to Stacker drives. Refer
to the description of CHKDSK in the ``Command Reference'' chapter
of DOSBook for more information.
Viewing Stacker Information in MS Windows
After you run Stacker, a Stacker pull-down menu is added to your File Manager the next time you go into MS Windows.
Warning: Never use the DR-DOS CHKDSK utility on a Windows 95 computer, even under DR-DOS. Use the Windows 95 CHKDSK tool only.
To be able to create a permanent swap file on a Stacker drive, you must display and change information about your system's virtual memory as follows:
1. In the Main group, choose the Control Panel icon.
2. In the Control Panel window, choose the Virtual Memory icon.
The Virtual Memory dialog box appears, which displays the current swap file settings.
3. Choose the <Change> button, to change the drive location, size, and type for the swap file.
The dialog box expands, enabling you change the settings. You can now select a Stacker drive to contain a permanent swap file. You cannot create a temporary swap file on a compressed drive, however.
For further information about MS Windows swap files, refer to the appropriate section of your MS Windows documentation.
NOTE: You cannot decompress a compressed diskette.
UNSTACK removes all the files from the compressed drive, decompresses them, places them back on the uncompressed drive it created when you originally compressed the drive, and deletes the STACVOL file. Refer to ``The Compression Process'' on page 12-6 for information about how Stacker compresses the drive.
Start decompressing a drive by typing the following at the system prompt, where d is the drive letter of the compressed drive:
UNSTACK d: <Enter>
You see a display that shows the progress made so far in decompressing the drive.
Using a Compressed Diskette on a Computer Without Stacker
When you use a compressed diskette on a computer on which the Stacker program has been installed, the compressed diskette is automatically mounted. If you want to use a compressed diskette on a computer on which Stacker has not been run, however, you will need to manually mount the diskette and make it available for use.
STACKER d: <Enter>If you need to unmount the compressed drive, type the following at the system prompt: