[ADSM-L] Backup stgpool waiting behind tape from backup stream

2007-08-17 17:48:56
Subject: [ADSM-L] Backup stgpool waiting behind tape from backup stream
From: "Schneider, John" <schnjd AT STLO.MERCY DOT NET>
Date: Fri, 17 Aug 2007 16:46:58 -0500
        We are running TSM under AIX.  We have a bunch of
Windows TDP Exchange clients that are pretty large (500GB), and
frequently run past their backup window and into the day.  They also
were frequently filling up the disk storage pool, so this past week we
moved their backups over to a virtual tape device (EMC CDL).  This has
solved the problem of them dominating our disk storage pool, and
migration and backup stgpools are faster as a result, too.

The problem:

1) The performance of the Exchange backup has not improved as we hoped
it would.  So our problem is probably not on the server side, but the
client side.  We have monitored network performance, and we aren't
constrained there.  The Exchange backups are only going to one virtual
tape drive at a time; there doesn't seem to be a 'resourceutilization'
parameter on the Exchange client.  Can they be made to backup to
multiple tapes at once?  I read about /buffers and /buffersize, but it
is not clear if those would help.

2) Another unusual circumstance is that the 'backup stgpool' for the
storage pool containing the Exchange data begins running before the
clients are done.  Sometimes the 'backup stgpool' get stuck waiting for
a tape mount, even though the tape is not mounted, and there are plenty
of tape drives available to be mounted.  I scratched my head about this
for awhile, but finally noticed that as soon as the Exchange client
finished it's backup, the tape that was waiting to mount indeed mounted
and the 'backup stgpool' proceeded from there.  Before you say "well,
duh!", let me point out that the tape waiting to mount was not in use by
the Exchange client, it had a completely different tape mounted.
However, the waiting tape was one previously mounted by that Exchange
client during it's backup.
        Does the client backup session keep all it's previous tapes it
has used reserved until the session completes?  Has anyone seen this
behavior before?

Best Regards,

John D. Schneider
Sr. System Administrator - Storage
Sisters of Mercy Health System
3637 South Geyer Road
St. Louis, MO.  63127
Email:  schnjd AT stlo.mercy DOT net
Office: 314-364-3150, Cell:  314-486-2359

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