ADSM-L

Re: progressive backup vs. full + incremental

2003-03-06 13:51:38
Subject: Re: progressive backup vs. full + incremental
From: Chris Murphy <cmurphy AT IDL.STATE.ID DOT US>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Thu, 6 Mar 2003 11:53:59 -0700
>I do not understand how you can get 50 clients on 1 disk pool to go to 20
>tapes.

Bill,

If I am wrong, someone will surely correct me, but what I think happens is
that when migrating the 50 clients from disk to tape, TSM will try to put
each one on its own tape (as collocate says it should).  So the first 20
clients each go to their own tape.  Then, when client 21's turn comes
around, TSM searches for a new scratch tape to hold this client.  If one
does not exist (because of MAX SCRATCH or simply out of scratch in the
library) TSM will go back and re-use the least consumed tape in that pool
for client 21 and migrates 21's data to that tape. Meaning that tape now
holds 2 clients.  Then for Client 22, the same thing happens:  it searches
for a scratch, when none are found, it finds the next least consumed tape in
the storage pool and uses it.  And so on...

>I would think that 50 clients on 1 (collocated) disk pool will
>take 50 tapes.

The Disk pool would not be collocated (because it would normally be a random
access pool, not sequential).  But, in our example, the destination tape
storage pool would be.

Hope that helps a bit!

Chris Murphy
IT Network Analyst
Idaho Dept. of Lands
Office: (208) 334-0293
cmurphy AT idl.state.id DOT us