It might be worth using a large disk storage pool that migrates to tape and
turn off collocation. Apparently ADSM will tend to migrate all the files
from a node at the same time. Here's a quote from the manual:

volumes in one storage pool, to provide clients with quick response to
backup and
recall requests. Then, as the disk storage pool becomes full, ADSM migrates,
or
moves, data to tape volumes in a different storage pool. Migrating files to
sequential
storage pool volumes is particularly useful because all the files for a node
are migrated
together. This is especially helpful if collocation is not enabled.



        -----Original Message-----
        From:   Warner, Alan [SMTP:awarner AT TI DOT COM]
        Sent:   Friday, May 14, 1999 2:22 PM
        To:     ADSM-L AT VM.MARIST DOT EDU
        Subject:        "True" Tape Capacity With Collocation?

        What is the optimal per cent utilization for a tape backup pool,
when
        collocation is turned on?

        We use 3590 tapes (10GB capacity, uncompressed).  On one server when
we do a
        QUERY STG command, it shows 37% utilitzation for backup tapes.  On
another
        server 52%, and on a third server 37%.  Our average amount of data
backed up
        per client is about 4GB.  Management says we're paying for too much
tape
        space that we're not using.  But we're also concerned to keep
restore times
        down to a minimum by not having client data distributed across more
tapes
        than necessary.

        Does anyone have a good rule of thumb (or any kind of a rule at all)
for
        optimal tape utilization with collocation turned on?

        Thanks,
           Alan