Eric,

The issues we had when we had caching turned on were:
1. Fragmentation of the the diskpool which led to a general slowdown in
processes.  This can be minimized if you have a regular schedule of
flushing the cache (turn it off and migrate down to zero).
2. TDP agents don't always play nice with diskpool using caching - some
algorithim issue that doesn't free up a big enough block and then kills
the backup when it runs out of room in the pool.

I'm assuming you are already multi-threading your stgpool backup and
migration, so the only suggestions I can offer are;
1. buy more tape drives and increase the multi-threads
2. buy tons of cheap disk and implement file-based stgpools.  This is
the approach we took and it cut our total housekeeping elapsed time by
75%.

Good luck!

Steve Schaub
Computer Storage Systems Engineer II
Haworth, Inc
616-393-1457 (desk)
616-886-8821 (cell)
Steve.Schaub AT Haworth DOT com 
"Trials are inevitable.  We can curse them and grow bitter, or harvest
them and grow stronger"


-----Original Message-----
From: Loon, E.J. van - SPLXM [mailto:Eric-van.Loon AT KLM DOT COM] 
Sent: Thursday, January 13, 2005 10:27 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Enabling caching to shorten housekeeping


Hi *SM-ers!
I'm currently struggling with the fact that I cannot run a backup
stgpool diskpool and a migrate diskpool (to empty it out for the next
client backup
cycle) sequentially no more. Migration would run well into the evening
and I would like it to be ready at 18:00 hours. I'm thinking about
turning on caching for my diskpool. If it works like I hope, TSM
migration empties out the diskpool, but leaving the actual data behind,
so a backup stgpool diskpool uses these cached copies, instead of
mounting all the tapes during a subsequent backup stgpool tapepool. In
that case, I can run migration and backup stgpool at the same time. Is
TSM working like this or will a cached object, once (logically)
migrated, be backed up from tape? Thank you very much for your reply in
advance! Kindest regards, Eric van Loon KLM Royal Dutch Airlines


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