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Changing the Compression Settings for Export

Created: 31 Jan 2006 • Updated: 29 Jul 2010
Jeremy_Hurren's picture
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You can adjust the level of compression that SVS applies when it creates a Virtual Software Archive (VSA). By adjusting this level, you can find a balance between performance and size. Jeremy Hurren shows us how to find the perfect balance.

If you have data that needs a different level of compression, you'll be happy to know there's a way you can change that (either per-layer or machine-wide). A perfect candidate would be my MP3 data layer which holds many gigabytes of data. Since the compression on MP3 files is infinitesimal, I choose to have them simply stored and not compressed at all to speed up the process.

The following setting will set the compression level machine-wide:

HKEY_LOCAL_MACHINE\SYSTEM\Altiris\FSL

CompressionLevel (DWORD) = 0-19 (5 is the default)

To set this for an individual layer, place the value under the following registry key:

HKEY_LOCAL_MACHINE\SYSTEM\Altiris\FSL\1

(replace 1 with the layer number)

The meaning of the compression level settings are as follows (all numbers in decimal), with higher numbers representing higher compression (and therefore slower operation):

0 No compression (same as 10).
1-9 Compress using the Deflate method.
10 No compression (same as 0).
11-19 Compress using the Enhanced Deflate method. May result in higher compression than standard Deflate, but may not be compatible with other ZIP utilities (nothing to worry about if your just importing and exporting with SVSAdmin or SVSCmd).

In my private testing on a layer with 170MB of MP3 files, I saw differences of 15-20% in compression time. The type of data you are compressing will affect this, so it may take a little trial and error to find the settings you like best.

For more information about modifying values in the FSL key, see the tip Auto-Closing Applications Running from a Layer.