Hello All,

We've been struggling with somewhat anemic backup performance from our
dedup storage pools to LTO4 tape over the past year or so.  Data is
ingested from clients and lands directly into our dedup pool, but doesn't
get deduplicated until the offsite operation is complete.
(deduprequiresbackup=yes)  Our dedup pool is comprised of 50GB volumes,
residing on a V7000 pool of NL-SAS drives.  The drives don't appear taxed
(utilization is consistently in the 30-40% range) but average throughput
from the storage pool to tape is only 100-100 MB/s.  This is starting to
present challenges for meeting the offsite window and I am stumped as to
how I might improve performance.

The TSM server is running on AIX and has four 8Gb paths to the storage,
running sddpcm.  Mountpoints containing the data are mounted rbrw and are
JFS+ volumes.  Our tape drives are running off of two dedicated 4Gb HBAs
and our backup DB throughput is excellent, averaging 350-400 MB/s.

For those of you that are running TSM dedup, how are you managing your
offsiting process?  Are you using a random devclass pool as a 'landing
zone' for backup/offsite operations before migration to the dedup stg? Are
there tuning parameters that you have tweaked that have shown improvement
in FILE devclass stg pools to LTO devices?

Any and all tips would be appreciated.  I've been through the parameters
listed in the perf guide and have allocated large memory pages to the TSM
server but I haven't seen much, if any, improvement.

Thanks!

Matthew McGeary
Technical Specialist
PotashCorp - Saskatoon
306.933.8921