Another comment... LTO numbers should probably be reported as being
LTO-1 or LTO-2.

LTO-1 max uncompressed is 15 MB/sec, max compressed is 30 MB/sec; LTO-2 max
uncompressed is 35 MB/sec, max compressed is 70 MB/sec. This assumes a
typical average compression ratio of 2:1, of course.

We use tapeutil under AIX (part of the Atape driver) to test the raw
throughput to tape with the rwtest option. May be possible to do similar
tests with other tools under other OSes.

We did this with the drive in question disabled in TSM then put an unused
blank tape (unlabelled and unknown to TSM) in the upper I/O station, closed
the door, then did:

# tapeutil -f /dev/smc0 move 769 257
(move from first I/O station slot to first drive in first frame; AIX knows
this drive as rmt0 in our case. **MAKE SURE YOU VERIFY THE ELEMENT ID FOR
DRIVE TO OS'S DRIVE NAME MAPPING OR YOU COULD DESTROY A TAPE WITH VALID
DATA ON IT!!!**)

# tapeutil -f /dev/rmt0 rwtest -b 262144 -c 20 -r 3
(do a destructive read/write test with a 256K block size factor, run for 20
blocks for each read test, 20 blocks for each write test, and do both set
of tests 3 times)

# tapeutil -f /dev/smc0 move 257 769
(put the tape back in the upper I/O station slot when done)

This destroys the ANSI tape label so it's best to do this on a previously
unused tape or you'll have to re-label (dsmlabel or 'LABEL VOLUME') it
afterwards.

And then, of course, re-enable the drive within TSM.

That gives us some idea of the raw potential. Then within TSM, I like to
see how fast it can push large files through to tape in a diskpool->tape
pool migration. Of course, this is also another 'test best case' scenario
because tape drives are more optimized for large files than for a number of
small ones, but it still gives you an idea about the upper bound of real
world performance.

Between the tests and TSM tape writes, it appears we get 22.5 MB/sec
sustained in compressed mode for LTO-1 drives. That's pretty decent; it's
halfway between the theoretical min and max for compressed mode, and we're
happy by its performance so we've got no complaints :-)

I should note that we don't really do database backups (well, we usually
export them to a SQL dump file in ASCII and back that up because the TDP
type tools are priced *outrageously* and our needs aren't _that_ pressing)
and that our data generally compresses well to tape -- we get an average of
2.24:1 hardware compression across the entire tape pool with a few bursts
of 3:1 and once, almost 4:1 compression for a LTO-1 tape.

The only way we get this kind of performance is to put a disk pool in front
of the tape drives... and we also limit it to two drives per SCSI bus
(because they're capable of peaking at 30 MB/sec or so in compressed
mode... so 2x30 = 60 MB/sec which means you need at least a Ultra2 SCSI
controller) to avoid contention or bottlenecks at the bus level.

The earlier tips about testing the FC setup was good, too.

-Dan