Stuart Liddle said:
>NO....Don't use Vault to duplicate from VTL to physical tape!!!

Looks like it's my week to disagree with you, Stuart. 
(Sorry.  I love ya' man!)

>We tried this, and in NB 5.1 MP6, Vault is a HOG!!  We were not able to
>Keep the drives spinning fast enough using Vault.  The best speeds we
saw >going to physical tape using vault was maybe 30MB/sec.  Usually we
got 
>around 10MB/sec or less....which is definitely not a good thing.

I've been able to get Vault to go MUCH faster than that. I would say
there are keys to doing it right.  The biggest one I see is that you
should either use multiplexing or not.  Don't mpx to tape (or virtual
tape) and then de-mpx when you copy.  VTL will suck just as bad as
regular tape when you do that.  So either preserve mpx when you dupe, or
don't mpx to your VTL (better).  Another key is having enough I/O
bandwidth in the media server to pull it off.

>What we ended up doing was using the built-in feature of our NetApp VTL
to
>do the cloning of the virtual tape to physical tape.  Now we are
getting
>much better performance of around 50 - 60 MB/sec.

Glad it got better. ;)

>The problem is that Vault has way too much overhead in doing the
copying of
>the data.

Again, I have to disagree.

>With the built in cloning function of the VTL, you just connect the two
>firehoses together and the data gets written from virtual tape to
physical
>tape.

There are also limitations to this approach.  While it removes the I/O
from the media server, you get a lot of wasted media if you eject your
copies every day.  In addition, the backup software has no knowledge of
the copy process, so if it fails, you're on your own for monitoring it,
etc. (It's not that I don't recommend this approach, I just wanted to
say that it does have limitations, perhaps the chief of which is that
Symantec will disavow any support on any issues you have.  Yuck.)

---
W. Curtis Preston
Author of O'Reilly's Backup & Recovery and Using SANs and NAS
VP Data Protection
GlassHouse Technologies