Hi all,

I'm currently testing TSM 5.5.4 on AIX 5.3 with an IBM XIV box.

When I use dd or other tools to copy data off the disk to tape (LTO4), we
get quite a good performance, 100 MB/s or better. Even when backing up data
on the XIV via shared memory directly to tape, we're quite happy, we can
read the data at over 100 MB/s for one backup job, and for over 200 MB/s for
two jobs. But, when TSM uses the XIV for DISK volumes, we're not in a happy
place, backing up data from one XIV to TSM with diskpool on another XIV, we
get about 55 MB/s per backup job, best case. Both XIV boxes are otherwise
completely idle. When migrating data of the diskpool to tape, it's the same,
no matter what we do, we don't even get close to the LTO4 native
performance, about 70 MB/s is the best I've seen, and usually it's less. The
TSM server is at that time only running the migration, nothing else.

The stragest thing we notice is that TSM seems to completely pause every so
often, no disk i/o, no tape i/o no cpu utilization, nothing for about one
second, and the it goes again. When I let two migration processes run, this
is less obvious, because one process continues while the other one pauses.

We've opened a hardware call with IBM to find out if there are any settings
on the hdisks or HBAs that we need to change, and even though we did get
some hints, and some performance improvement out of that, we fell that TSM
should be able to do a lot better.

Does anyone else have experience with XIV as a diskpool? and if so, what
sort of performance do you see?

--
Met vriendelijke groeten,

Remco Post, PLCS