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