Yep, had the same problem with iSCSI volumes.  Try turning off
directio with the following undocumented dsmserv.opt option.

directio no

Gary Bowers
Storage Architect
Itrus Technologies

On Mar 1, 2010, at 10:24 PM, Roger Deschner wrote:

We have a devtype=file stgpool that is on NAS disk, accessed via NFS,
and we're getting very slow performance with TSM reading or writing
it.
In a test, the Unix cp command moved data about 5 times faster than
TSM
Migration.

I have been adjusting the number of migration processes up and down,
while watching network data flow numbers with topas, trying to get
clues. There comes a point, that processor wait time goes over 90%,
and
then it hits a wall. The maximum seems to be about 10Mbytes/sec on a
point-to-point network consisting of three trunked GigE connections. A
single Unix cp command could write about 48Mbytes/sec, to the same NFS
filesystem, on the same NFS server, across the same network.

Anybody else faced this kind of issue?

Roger Deschner      University of Illinois at Chicago     rogerd AT uic DOT edu
              Academic Computing & Communications Center