ADSM-L

Re: Compression

2000-02-01 02:54:44
Subject: Re: Compression
From: "Mauro M. TINELLI" <Mauro.TINELLI AT ST DOT COM>
Date: Tue, 1 Feb 2000 08:54:44 +0100
Paul,

I agree with you. Where to compress is more an issue of tuning the whole
*SM environment, hardware, network, etc.

Mauro, STM

> At 04:21 PM 1/31/2000 -0500, Johnson, Chris E. wrote:
> >All,
> >
> >Is there any advantages or disadvantages to using "Compression" with
how it
> >relates to Nodes in *sm?
>
> I have to take an opposing view to Kelly's on compression.  I would
argue
> that you should enable compression at the client, unless you have a
> particularly slow client system.  Running single-backup performance
tests
> will probably not show any differences between compression and
> non-compression.  However, logically it just makes sense to compress
data
> as early in the process as you can, and to distribute the overhead of
> compression out to the client systems, if possible.  Kelly may be
correct
> that tape drive compression is as good as *SM compression.  However,
IMHO,
> doing compression at the tape drive misses performance/thruput
advantages
> that you could have gotten if doing compression at the client.  Backup
data
> originating at a client system will take the following path in a
typical
> *SM environment:
>
> 1. Client System
> 2. Network
> 3. *SM server RAM
> 4. *SM server disk storage pool
> 5. *SM server tape storage pool (migration from disk)
> 6. *SM server tape storage pool (reclamation)
>
> Using client compression should yield performance/thruput advantages in
> steps 2-6, while using tape compression will only yield performance
> advantages in step 6.  I don't know if using tape drive compression
will
> slow down tape I/O, but I doubt that it will, so that shouldn't be a
factor.
>
> As Kelly says, if you have enough network bandwidth, then step 2
doesn't
> matter, but step 4 could still make a difference.  In any case, why NOT
use
> client compression?  Most systems are fast enough now that compressing
data
> doesn't cause any performance problems on the client system.  If you
think
> you might someday run out of resource in any of steps 2-4, then you
might
> as well use client compression.
>
> my 2 cents.
> ..Paul
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