Veritas-bu

[Veritas-bu] Implications of turning off s/w compression?

2002-04-02 10:27:08
Subject: [Veritas-bu] Implications of turning off s/w compression?
From: Dave.High AT veritas DOT com (Dave High)
Date: Tue, 2 Apr 2002 07:27:08 -0800
Answers inline

__________
dave high
VERITAS Enterprise Consulting
702.683.7733
 
Unix IS user friendly, it's just VERY picky about who it chooses as friends
 

> -----Original Message-----
> From: Richard.Hall [mailto:richard.hall AT ingenta DOT com]
> Sent: Tuesday, April 02, 2002 6:31 AM
> To: veritas-bu AT mailman.eng.auburn DOT edu
> Subject: [Veritas-bu] Implications of turning off s/w compresion?
> 
> Recent discussion here has convinced me that we should never have set up
> NBU s/w compression in the first place. ("Told you so"!!)
> 
> Before we turn it off ...
> 
> 1) will this affect recovery from existing images?

No

> 
> 2) or mess anything else up?

No

> 
> 3) (For academic interest only, and to make sure I understand what is
>    going on)
>    Since our DLT7000s are currently managing ~5Mb/sec, I assume that the
>    data is currently compressed on the client side, not decompressed again
>    on the server side, and the drives are (roughly) achieving no further
>    compression. And that, other things being equal, I can now expect to
>    see them managing 10 Mb/sec, but with no reduction in backup time.
>    Except perhaps in the tail of the backups, where the number of jobs and
>    the total data rate is falling.

What you should see is a bit more compression due to hardware compression
being more efficient than software compression and you *should* see the
backups speed up a bit all things being equal. Software compression
compresses on the Client (like you said) and then sends the compressed
packets to the server. Sending a stream is more efficient. Speed could be
20% or so better but that depends on your LAN. 

Cheers, 

dave

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