David,
   I originally set my TS7510 to the default 300GB vtape size with
dynamic allocation where only 5GB is initially allocated and the space
is grown as data is written.  I found out that once data is written to a
vtape, the vtape will retain that size until it is scratched AND THEN
written to again - at which point it will revert to the initial size.
I had a bunch of scratch vtapes that were consuming 300GB of space on
the VTL because they were not written to AFTER they had been scratched.

   I now use 60GB 3592J vtapes on my TS7520 and it seems to work well.
   By the way - If you also use dynamic allocation, make sure you patch
your TS7520 to Version 05F which was just released yesterday.  I have
experienced numerous system hangs because there is a bug that causes a
race condition when two or more vtapes are being resized simultaneously.

Cheers,
Neil Strand
Storage Engineer - Legg Mason
Baltimore, MD.
(410) 580-7491
Whatever you can do or believe you can, begin it.
Boldness has genius, power and magic.


-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
David E Ehresman
Sent: Thursday, November 29, 2007 9:01 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: [ADSM-L] Sizing virtual tapes

How large are you making the max size of your virtual tapes?  Why?

I let my TS7520 emulating 3592E tapes default to a max size of 460GB but
I'm starting to think a smaller size would make more sense.  The median
size of occupancy for my nodes is around 40GB so I'm thinking that might
be a better max size to facilicate reclamination.

David

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