No it doesn't, as the DDR cleaning cycle will only clean those blocks
that can be erased since the data no longer exists. Data that is still
duplicated somewhere on the DDR is left alone. Those blocks that can be
cleaned are less likely to be duplicated since they can be cleaned so
quickly, stale data, on the other hand, like file system files, will be
around forever.

Part of the problem in going with the VTL option of the DDR is that you
have to still manage tape in that you want a very small scratch pool
tape rotation to maximize your DDR file system cleaning cycle. With the
NAS option this would all be transparent, but with the VTL option the
data on a virtual tape is only marked available for cleaning when the
file is truncated. The best way to truncate the file is to run a quick
erase, which essentially re-writes the headers of the virtual tape.


Jason Ellis

-----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 tburrell
Sent: Tuesday, July 01, 2008 1:16 PM
To: VERITAS-BU AT mailman.eng.auburn DOT edu
Subject: [Veritas-bu] Quick Erase Question


Maybe I'm missing something here, but doesn't aggressive space
reclamation on a DDR run counter to the point of the thing?  The more
blocks you have on there, the better the odds that the next block will
be a duplicate.  Obviously you can't keep unused blocks forever, but
otherwise I would think you would want to be pretty moderate in how you
go about this.

Are you really running that lean on the DDR?

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