Mike,

Why not have the JBOD pool between your DASD pool and tape, then cache it?
If it's big enough to hold 3 days worth of data, you're set.


                   -- JBOD --  Tape Primary Pool
                 /      |       |
Primary Pool ---<       |       |
                 \      |       |
                   -- Tape Copy Pool

Backups come to Primary pool, your fast DASD.  It is then migrated to the
JBOD pool, where it is cached when it migrates to your Tape Primary Pool.
All three pools are backed up to the Tape Copy Pool.  If the JBOD pool is
big enough to hold 3 days worth of data, and a restore comes in, the data
will be there to restore.  If the data has been flushed from the cache, it
will be on tape, so at least it's there.  And by backing up all three
pools, you have solid coverage for any issues.

Nick Cassimatis
nickpc AT us.ibm DOT com

He who laughs last has a good backup.