When we upgraded we needed a new library defined in TSM to use the 3592's
with different private/scratch categories, and device class's, drives,
etc..
Not a different 'logical' library defined on the 3494 library manager.
That may have worked too, but it depends on how particular you want to be
as to which
drives/slots are available to each host connected to the library.

3592's have been good.   So far after 9 months use of 500 tapes and 6
drives.
2 tapes had I/O problems, no serious problem in data lost,  TSM's  'restore
volume' cleaned it up in minutes.
some drives have just needed code upgrades to remove minor problems.
One had 'clean me' displayed permanantly, it went way after that.
One was replaced, but it was bad from the factory on initial installation.

Try to do the code upgrades for the drives from the Host's fiber/scsi.
When the IBM SE pushed it via the Library manager it took hours instead of
minutes.

The web interface on the upgraded library manager is great!
No longer do you have to login to the library manager console to find out
why 'operator intervention' is required...
You can check it from your desk and decide to call in IBM to fix the
problem or just unload the tapes that wanted to come out of the I/O slots.

My biggest issue is that the server we have connected to those 6 drives
can't push data fast enough to them, they can go much faster!

Matthew Glanville
Eastman Kodak