I've used STK 9840 and 9490 drives under AIX and on Pyramid systems, with good
success.  This was NOT using *SM, though...it was using two other backup
software products.

I think there is a (microcode-controlled) option in both the 9840 and 9490's
to operate in "native" (STK) mode or IBM emulation mode.  We always used STK
mode, therefore atape drivers were not used...we used the IBM OST (Other SCSI
Tape) drivers under AIX.  We also used the drivers produced by Gresham
(formerly Open Microsystems) located at
http://www.greshamstorage.com/products/advan.html

Their Advantape drivers were well supported (with a nice trace facility), and
provided a significant (100%) performance improvement on Pyramid (but only
marginal improvement on AIX 4.3.2)....they might be worth a look...they did
well for us.

Although the increased data transfer rate was nice on the 9840's, the biggest
gain was mount time....a 64 gig database backup that formerly took 80 9490
tapes (and 5 hours) lost about an hour (20%) waiting for tape mounts.  Same
backup on 9840's used 2 tapes and 2 mounts.....  so we had a 20% improvement
via tape mount elimination alone.

One "secret" we found with ultra-scsi cards (pci cards in both Silver nodes and
Winterhawk II nodes):  These cards have an internal scsi cable connection plus
an external cable connection.  Smitty/dev/scsi adaptors/change allows you to
set ultra-scsi speed for the external connector ....this defaults to "disable"
(the assumption is that if we're using external cables, then we might not meet
ultra-scsi requirements).  You must set this manually to ENABLE, else you do
not achieve ultra-scsi speed.   Until we discovered this, our benchmarks with
9840's were quite disappointing!    This also applies to our 3590 drive
connections.

BTW: if anyone can recommend optimum settings for other options for these cards
(eg: Number of DMA bursts per PCI bus ownership, DMA bus memory length, Target
mode bus memory length), I'd be interested to hear them.  Both of my tape drive
vendors have responded with "huh?" when asked for their recommendations!

Similarly:  does anyone have recommendations re daisy-chaining two ultra-scsi
drives on one card?  Will 3590 "B's" or "E's" perform ok if we put two on each
ultra-scsi card?

hope this helps....JRS.