Re: [ADSM-L] Why virtual volumes?

2007-08-22 19:48:13
Subject: Re: [ADSM-L] Why virtual volumes?
From: Stuart Lamble <adsm AT CAROUSEL.ITS.MONASH.EDU DOT AU>
Date: Thu, 23 Aug 2007 09:46:17 +1000
On 23/08/2007, at 7:29 AM, Nicholas Cassimatis wrote:
And a TSM DB Backup takes (at least) one volume, so with physical
cartridges, that's a whole tape.  With VV's, you're only using the
capacity of the backup, which is more efficient on space.

At the cost of some reliability. What happens if the particular tape
the virtual volumes are on goes bad, and you're in a disaster needing
a DB restore?

I'd rather spend the extra money on tapes and know that if something
goes bad, we'll at least be able to recover some of the data ...

(I'm seeing installations getting over 2TB on the new 3592/TS1120
drives - for a 60GB TSM DB Backup, that's VERY wasteful).

Well, why not do what we're doing soon? We currently have some 1200
LTO2 tapes, and are in the process of migrating from LTO2 to LTO4;
(some of) the LTO2 tapes will be kept in the silo for database
backups (along with a single LTO2 drive for writing to those tapes.)
There's another silo with LTO3 volumes; some of the LTO2 tapes will
be put into that silo for exactly the same reason (LTO3 drives will
write LTO2 tapes, so there's no issue with needing an LTO2 drive in
that silo, at least for the time being).

Call me a conservative fuddy duddy if you want, but I prefer to keep
the TSM database backups as simple as possible.

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