On Jul 31, 2007, at 11:59 PM, Stuart Lamble wrote:

I am not going to enter into a debate about the relative merits of
raw volumes versus files on filesystems, as I have insufficient
direct knowledge to judge either way (I'm trusting a more senior
colleague to make the right call there. :)

I'll jump in anyway...
The pure simplicity of RLVs makes them a joy to implement, compared
to the time-consuming work entailed in implementing a TSM volume
within a file system.  Their simplicity almost makes them mandatory
where rapid disaster recovery is vital, as there's far less TSM
server set-up time getting in the way of recovering your
organization's functionality.  However, RLV access amounts to
unbuffered I/O, and that exacts a performance penalty relative to
file system volumes, where read-ahead provides a nice boost when the
task at hand involves stepping through the volume.  I use RLVs, and
it's apparent that Migration is relatively sluggish, as in a disk
storage pool struggling to stay empty enough to handle all the
incoming client backup data so as to prevent some backups having to
go directly to tape.  The TSM Performance Tuning Guide cautions about
this.

  Richard Sims, Sr. Systems Programmer at Boston University