Kelly,
I have 500+ clients (420 Unix, 30 NT & 50 netWare & 7 Vaxes) to backup
each night with 1 ADSM server and my diskpools only act as cache to the
tapepools. Compression is the default setting on each client with just
few exceptions (SAP/Backint - Informix/OnBar). It can't simply work
without client compression. On my view/case, distributing the workload,
is a step towards network-free, server-free backups.
Mauro, STM
> Paul,
>
> I agree with your observations. However, I can't rationalize them with
the
> lack of elapsed time backup improvement. Yes, compressing earlier
rather
> than later makes sense. But why, then, don't we see an improvement in
> overall backup times?
>
> I really like compression to keep the overall disk storage pool
utilization
> low. That's a real good reason to do it, if you don't have enough disk
> pool.
>
> How about somebody that compresses everyplace giving us their real
world
> experiences?
>
> Kelly J. Lipp
> Storage Solutions Specialists, Inc.
> PO Box 51313
> Colorado Springs CO 80919
> (719)531-5926
> Fax: (719)260-5991
> www.storsol.com
> lipp AT storsol DOT com
>
> -----Original Message-----
> From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU]On Behalf Of
> Paul Zarnowski
> Sent: Monday, January 31, 2000 3:22 PM
> To: ADSM-L AT VM.MARIST DOT EDU
> Subject: Re: Compression
>
>
> 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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