Look at the MAXSCRATCH value for the storage pool. You don't need another
350 tapes.
You can use MAXSCRATCH to strike a balance between having a zillion tapes or
no collocation at all.
The simplest explanation: If you set maxscratch to 100, TSM will put each
client on its own tape until it hits 100 (maxscratch) tapes, then it starts
putting 2 on a tape, then 3, etc.
What that does is give you collocation, in that each client's data is on a
minimal set of tapes, but you get better tape utilization. (After all,
setting MAXSCRATCH is the ONLY way people can manage who have more nodes
than library slots.)
And it works very well from a performance point of view. When you get ready
do to a restore for client1, it costs you very little to skip over the data
for client2 that is on the same tape (after all, you are skipping over some
inactive data for client1 anyway). The point is that you get your client's
data on a minimal set of tapes.
BTW, you can just set maxscratch and set collocation ON. You can do MOVE
DATAs to force the old data to get moved back to collocated tapes as you get
around to it, or let it happen gradually as reclaims occur.
The only drawback to using MAXSCRATCH is that you have to monitor it
regularly. As you get more total data in the library, or as your data gets
dispersed onto partially-used tapes waiting to reclaim, you will have to
increase MAXSCRATCH. If you don't, as your tapes fill up TSM will start
putting more and more clients on the remaining tapes below MAXSCRATCH until
you are effectively un-collocated again.
************************************************************************
Wanda Prather
The Johns Hopkins Applied Physics Lab
443-778-8769
wanda_prather AT jhuapl DOT edu
"Intelligence has much less practical application than you'd think" -
Scott Adams/Dilbert
************************************************************************
-----Original Message-----
From: brian welsh [mailto:brianwelsh3 AT HOTMAIL DOT COM]
Sent: Wednesday, February 19, 2003 3:43 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Question about collocation on/off
Hello,
AIX 5.1, TSM 4.2.2.8 en 3494 ATL with 700 volumes (used about 620 volumes),
and about 300 nodes. Three months ago we turned collocation off because we
have about 200 client-nodes with less then 3 GB's data stored, and every
node was using min. 1 tape, so we had a lot of tapes with low utilization,
long migration.
Now tape-utilization is much better, migration is much faster, but yesterday
there was a restore of an web-server (WinNT) and we restored almost 2 GB and
it took 6 hours and there were almost 70 tape-mounts.
Before we set collocation off such restores took half an hour. Now we are
thinking of setting collocation back on, but that implies we have to buy and
checkin about 350 new tapes, because move data will take weeks or more.
Now I was wondering how other sites are dealing with collocation, and what
are they doing to get better results during restore, when collocation is
off.
We are thinking of make a full back-up once a month to get data of one
client on less (or one) tape(s), or putting collocation back on, or...
Curious to your reaction!
Thanx,
Brian.
_________________________________________________________________
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