There isn't really any way to do this since it is impossible to know,
generally, how much data can fit on each tape.  You can make some
calculations based on tape utilization of full tapes in the library to
determine average capacity of a tape and apply this to all other tapes.  TSM
sort of does this with it's estimated capacity number on the pool.  However,
if maxscratch is set larger than the number of tapes the library holds, it
won't help with your original question.

Monitoring is the key. As everyone knows, a too small library is the bane of
TSM administrators.  If you sense you are in this minority, you're stuck
with removing full tapes from your library and replacing them with scratch
tapes.  Mr. Murphy will then rear his ugly head and want the tape you just
removed, but there isn't a way around that problem.

I've toyed with the idea of limiting my tape pool to something less than the
library capacity and using an overflow pool to catch data in the event I
fill 'er up.  I can then monitor volumes in the overflow pool.  If there is
a volume in the overflow pool, I know the tapepool is full.  I can add
scratch volumes to the pool, and then move the data from the overflow pool
back to the tapepool.  I've never set this up, but it would work.

We're working on some additions to our STORServer Manager product to help
gauge the capacity of storage pools and volumes.  Nothing to look at yet,
however.

The easy answer is to buy a bigger library and not worry about it.

Kelly J. Lipp
Storage Solutions Specialists, Inc.
PO Box 51313
Colorado Springs CO 80949-1313
(719) 531-5926
Fax: (719) 260-5991
Email: lipp AT storsol DOT com
www.storsol.com
www.storserver.com