Re: server restore behavior

2006-08-18 12:42:18
Subject: Re: server restore behavior
From: Laura Mastandrea <lmastand AT CHOOSEBROADSPIRE DOT COM>
Date: Fri, 18 Aug 2006 11:41:04 -0500
We just had a DRP test and this question came up and I'd like confirmation
that I'm reading your remark correct.  TSM, on a restore, will mount a tape
once and take all the files off of once?



                                                                    Sent by

           "Kauffman, Tom" <KauffmanT AT NIBCO DOT COM>  on  08/18/2006 11:30 AM
           "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
         Re: [ADSM-L] server restore behavior

           Please respond to
        "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>

TSM will mount and start as many sessions as possible, and the rest will
be in 'wait media' state until the tape they need (or a tape drive)
becomes available. Given your scenarion, you may have one session
reading tape and the other four waiting for access to the same tape.

When the first session has retrieved ALL the files it needs from the
first tape, it will go to the second (if not in use) and the session
that has been waiting the longest will now get access to that first

Tom Kauffman

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Troy Frank
Sent: Friday, August 18, 2006 12:23 PM
Subject: server restore behavior

This is more of a curiosity question than a problem.  In a
multiple-client restore scenario where you start up say 5 restores at
once from different nodes (with 4 tape drives, and resourceutilization
set to 4 on nodes), how does the server process the request?
Technically, data from all 5 nodes are probably on a lot of the same
tapes.  Does it....

A) mount each tape exactly once, getting all data for all running
restores off that tape before unmounting.

B)  Process the restores relatively serially for each node, giving each
all 4 drives until completed.  Unmounting/remounting the same tapes
multiple times.

C)  Only give each node 1 tape drive to work with, which will
effectively ellicit behavior very similiar to option B.

Or does it do something different than any of these?

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