And you don't get the space back on a DSU until you expire the image.
So what?  I also argue that what Steve is asking for isn't necessary.
(I think he's MAKING it necessary by oversubscribing, but that's not the
VTL's fault.)

Oversubscription aside, once his tapes are expired, the space taken up
by those tapes is immediately available for reuse.  The next time the
tape gets written to, it will delete all pointers to the space taken up
by that tape.

As to the VTL vs disk debate, I still think you should bring in all disk
devices and let them duke it out before excluding an entire category of
them.  You're going to exclude a lot of really good products if you just
"no VTLs."  

Remember that saying "I don't want a VTL but I do want de-dupe" means
that you're going to use NAS.  While that will meet a whole lot of needs
for a whole lot of people, there's also some really big backups that
need a lot more than you can push over IP.  For those backups, you're
going to want a block transfer protocol (i.e. SCSI), and for that,
you're currently going to be buying a VTL.  (Unless you're just going to
buy a non-deduped disk in which case I'd say you're REALLY wasting your
money.)

---
W. Curtis Preston
Backup Blog @ www.backupcentral.com
VP Data Protection, GlassHouse Technologies 
-----Original Message-----
From: veritas-bu-bounces AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of Clem
Kruger
Sent: Saturday, September 22, 2007 4:24 AM
To: VERITAS-BU AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu] Script to label expired tapes in a VTL

Hi Steve,

This is the downer on VTL's. You do not get your "tape" space back
automatically. It is for these reasons I recommend that one never go
VTL's. NetBackup 6.0 and 6.5 allow disk to disk backups; the images are
easily replicated to an offsite facility.

The time for all "tape" has come and gone. The de-duplication facility
in 6.5 makes life even easier. Why VTL's (which does SCSI emulation)
when you and use disk which is faster and has more protection?

Clem.

-----Original Message-----
From: veritas-bu-bounces AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of swaltner
Sent: 21 September 2007 17:32 PM
To: VERITAS-BU AT mailman.eng.auburn DOT edu
Subject: [Veritas-bu] Script to label expired tapes in a VTL


We deployed a VTL last month, which has been working very nicely. This
is in a NetBackup 5.1 environment with the VTL attached to our Solaris
based master server as well as to our NAS server for local NDMP backups.
One thing I'd like to do is over-subscribe on the back-end storage, but
before I do that I'd like to automate the process of freeing up the disk
space used in the VTL when a NetBackup tape is expired. Just curious if
anyone has already written such a beast and would like to share with me
as a starting point.

If not, I suspect I'll use the following logic:

- Every day (at noon??), query the robots defined in the VTL and keep a
record of tapes that are allocated.
- When a tape goes from allocated to non-allocated from one day to the
next, use a command like the following to erase the tape's contents:
bplabel -erase -o -d dlt -m VTL123

This would write a small label at the beginning of the virtual tape,
causing the VTL to drop all the other data that had been stored on the
tape.

Any reason this wouldn't work? Any gotchas with writing this script that
I should look out for?

Steve

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