On Wed, May 17, 2006 at 09:20:58AM -0500, Jason L Tibbitts III wrote:
> Has anyone given thought to automatically disabling compression on
> filesystems where compression performs poorly?  I have a large number
> of filesystems to back up and my "compression ratio" should be an
> "expansion ratio".  There are some filesystems where it helps quite a
> bit, however.  Rather than turning it off globally I could disable it
> on selected filesystems, but going through the whole list is time
> consuming.
> 
> Is it possible for amanda to consult the backup history and check the
> past compression performance when deciding whether or not to enable
> compression on a particular filesystem?
> 
> Note: I'm willing to hack at this if someone can give me some
> pointers.
> 

I don't think an automatic tool is needed.  The compressibility of
a DLE doesn't change often.

However a tool to check and recommend might be useful.  And it could
be entended to take action automatically if desired.

Things to consider/sources of input data:

 - curinfo directory has "info" file showing up to 3 most recent
   compression ratios for full and incremental.  You could grep for
   these lines.
 - same data is available from amadmin "info" cmd in a different form.
 - amadmin "disklist" cmd can show whether compression is turned on.

-- 
Jon H. LaBadie                  jon AT jgcomp DOT com
 JG Computing
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