Our setup:
TSM 5.4.1.2 Server on Linux, a 19TB disk pool dedicated to the management class 
for the NAS node. The disk pool is largely made up of 1.8TB volumes on a RAID5, 
the maxfilesize is set to 'nolimit', highmig=100, lowmig=99.  The NAS is a 
BlueArc, according to the trace:
NAS Vendorname:     BlueArc Corp.
Productname:    Silicon Server NDMP.
Revisionnumber: 6.1.
Hosttype:    BOS.
Versionnumber: 6.1.

The filesystem in question:
fsName=/__VOLUME__/cifpilot1, fsType=WFS, fsId=2, fsCap=10Tb, fsOcc=8650Gb

When I perform a backup of that filesystem (backup node XXXXXXXXXXXXX.umich.edu 
/__VOLUME__/cifpilot1 toc=yes mode=diff), rather than go to the empty disk 
pool, it immediately goes to tape.  This is causing a problem because the job 
is getting preempted when the scheduled migrations occur on the other servers 
at 7am.  Other smaller filesystems (0.4 and 5TB, respectively) backup to disk 
just fine.
I've moved the backup as early as I could to try and get it to complete before 
migrations, but that's not working anymore.  I need to figure out why this 
backup is going to tape rather than to disk.

Anybody have any ideas?

-
Cameron Hanover
chanover AT umich DOT edu

"Necessity is the plea for every infringement of human freedom.  It is the 
argument of tyrants; it is the creed of slaves."
--William Pitt, House of Commons, 11/18/1783