>> On Tue, 20 Jun 2006 10:08:59 -0500, John Monahan <JMonahan AT COMPURES DOT 
>> COM> said:

> I did find and read that guide, although the information now seems a
> little dated (10/20/2003).  It looks like it hasn't been updated
> since EMC came out with their own VTL, which would make sense if
> they are pushing people towards that solution for disk based
> backups.  The whitepaper isn't available on Powerlink, but is
> available on a few other sites found by searching.  If you are aware
> of a newer/updated version than the one I have, please let me know.
> I also read and recommend the engineering whitepaper "EMC Clariion
> Best Practices for Fibre Channel Storage".

I had an excellent conversation with an EMC tech rep. It only took
about 5 minutes for us to reach the shared conclusion that their VT
solution (which, recall, involves no tape) was a waste of effort if
you had TSM and FILE devclasses.  This candor impressed me.

> I just made one large striped LV.  I was leaning towards the
> multiple LUNs and multiple LVs route as well so I would have
> multiple queues, threads, etc. to the disk, however, the EMC
> recommendation is to use one very large LUN per RAID group for
> sequential based disk backups to SATA disks and I concur.  [...]


Did you do any FILE devclass work?  It sounds as though your miserable
performance was head thrashing, which we'd get in multiple LV DISK
devclasses, and also in FILE devclasses.  Darn. :)


- Allen S. Rout