Saving Disk Space with File Compression


Enabling File Compression

By default, file compression is enabled at the volume level when a volume is created. If you do not enable file compression when you create a volume, you can subsequently enable it using the SET utility. Once file compression is enabled for a volume, you can turn it on or off for individual files and directories by setting compression attributes with NetWare Administrator or FLAG.EXE. For background information, see File Compression.

See NetWare Administrator or FLAG for a general description of those utilities.

IMPORTANT:  Do not use file compression on a CD-ROM volume.

It isn't necessary to separate applications from data for file compression, because the SET parameter named Days Untouched Before Compression can eliminate the compression of applications that are used regularly. This parameter specifies the number of days that must pass without access to a file before the file can be compressed. The parameter uses the date the file was last accessed to gauge whether a file should be compressed or not.

To avoid the overhead of uncompressing files that don't compress well, the system calculates the compressed size of a file before actually compressing it. If no disk space will be saved by compression, or if the size difference does not meet the value specified by the SET parameter named Minimum Percentage Compression Gain, the file is not compressed.

For a file to be uncompressed, there must be enough free space on the volume to accommodate the uncompressed file size.

For instructions on setting file compression for volumes, directories, and files, see Setting File Compression Attributes.


Disabling File Compression

File compression is enabled and disabled at the volume level.

If you do not enable file compression when you create a volume, you can subsequently enable it using the SET utility. Once enabled, however, file compression cannot be disabled on the volume unless you re-create the volume.

You can temporarily suspend file compression using the SET command's Enable File Compression parameter. (See SET for a general description of the SET command.)


Setting File Compression Attributes

To set file compression attributes for a volume (including enabling compression), use NWCONFIG or SET (see NWCONFIG or Using SET to Set File Compression Attributes for Volumes).

To set file compression attributes for a directory or file, use NetWare Administrator (see Using NetWare Administrator to Set File Compression for a Directory or File), or FLAG (see FLAG).

To view file compression attributes for a directory or a file, use NetWare Administrator or FLAG.


Using SET to Set File Compression Attributes for Volumes

Use SET to set file compression attributes for an entire volume. File compression SET parameters do not affect volumes on which compression is disabled.

IMPORTANT:  Do not use file compression on a CD-ROM volume.

To change SET parameters, execute the SET command at the server console prompt.

The following list identifies SET command parameters that affect file compression. The settings apply to all files and directories in compression-enabled volumes on the server. For the function and range of values associated with each SET parameter, see SET.


Using NetWare Administrator to Set File Compression for a Directory or File

Use NetWare Administrator to set file compression attributes for individual directories or files. The attributes are Immediate Compress (IC) and Don't Compress (DC).

NOTE:  Compression is a usually a low priority process thread because of compression's impact on performance. If you flag an item for immediate compression during peak system usage, performance may deteriorate.


Prerequisites


Procedure

  1. In NetWare Administrator, select the file or directory for which you want to set compression attributes.

  2. From the Object menu, choose Details.

  3. Choose Attributes.

  4. From File Attributes, choose Immediate Compress or Don't Compress.

  5. Choose OK.


Suspending File Compression

Use SET command's Enable File Compression parameter to temporarily suspend file compression for a volume. (See SET.)

The MONITOR command can also be used to change file compression parameters. (See MONITOR.)

While file compression is suspended, files that would have been compressed are queued and compressed when compression is re-enabled.