My gut feel (and the advice from an IBM TSM support guru here in
Australia) is to have 3 or 4 volumes per spindle for database disks.
Those "spindles" may be logical RAID5 arrays as in a shark, etc. The
reason, is to allow 3 or 4 outstanding requests to each disk, which
the disk can then re-order to minimise over-all seek times. Since the
TSM DB is primarily hit with random read I/O, this *should* be a win.

Of course, trying to test this and come up with some hard numbers
would be a right-royal PITA... The Sun TSM servers I manage used to
have the "big & few" DB volume design, but I have since migrated to
3 volumes per spindle, mirrored in TSM design. I can't say if
performance is greatly improved, and I have no numbers, but it
"feels" faster. Makes me wish I had recorded expiration start and
finish times (although, that's probably a single thread in TSM and
won't prove anything)...

Since log volumes are sequential read-write, this does not apply to
them. And storage pool volumes? That depends on a whole bunch of
other factors.

Cheers,
--
Paul Ripke
Unix/OpenVMS/TSM/DBA
101 reasons why you can't find your Sysadmin:
68: It's 9AM. He/She is not working that late.
-- Koos van den Hout