We run ours at 25% except one pool that we reclaim at 5%.  Really, 5%.
We ran incrementals direct to VTL with 30 servers backing up at one
time, each to a separate virtual tape.  Pool utilization was about 42%
but %Migratable was at 93%.  All those virtual 100 GB tapes with 1.2%
utilization messed with the statistics.  We had incremental backup
failures when automigration kicked in.  The data went to the secondary
storage pool and we didn't have enough physical drives to handle the
backup load.  I used 'move data' commands to consolidate the data but
instead of stacking data on used tape it started writing to
recently-emptied tapes.  We've reverted to backing up incremental data
to disk and migrating to VTL.

More whining available upon request.

Jim Schneider

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Andy Huebner
Sent: Wednesday, June 04, 2008 9:47 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] VTL and TSM - Hyper Reclamation ????

We run ours at 50%.  One thing to consider is whether your server and
VTL will have the bandwidth to reclaim at those percentages.

Andy Huebner
-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Richard Rhodes
Sent: Tuesday, June 03, 2008 8:08 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: [ADSM-L] VTL and TSM - Hyper Reclamation ????

We are investigating VTL's as a replacement for our 3494 libraries.
A vendor was describing their sizing calculations and
assumptions.  One of their assumptions BLEW US AWAY!!  The
vendor recommended that reclamation  be done
on VTL volumes at a 20-30% Reclamation Percentage.  YES,
that's right, they recommend that a volume get reclaimed
when only 20-30% of the data is expired.  They claim that
this is possible due to the efficiencies and speed
of the VTL, and thus allow us to run at a much higher
average utilization.  The argument is that with a
higher average utilization we can purchase less disk, and
thus a less expensive VTL.

Currently, for our tapes, we reclaim at 55-60%.

Q)  Has anyone every heard of performing
reclamation at a percentage as low as 20-30%?

Q)  Is anyone with a VTL actually performing
reclamation at 20-30%?

Thanks!

Rick


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