If at all possible, yes.
But you could get into a scenario where one session is waiting for a
tape drive, but not the tape in question, AND it has been waiting longer
than any other session. If so, the tape will dismount and the other tape
will mount for the long-waiting session. And the first tape will remount
later, for some other session.
But for any given session, the tape will mount once unless pre-empted by
a higher priority process (IIRC, the only process with a higher priority
than a restore is a TSM database backup).
Back in our first three years of D/R we had four DLT-7000 drives in our
hotsite contract with no library, so we configured a 'manual' library
with 4 tape drives. We got intimately acquainted with the TSM tape
handling process as a result.
Tom Kauffman
NIBCO, Inc
-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Laura Mastandrea
Sent: Friday, August 18, 2006 12:41 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: server restore behavior
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?
thx
To
ADSM-L AT VM.MARIST DOT EDU
cc
From
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>
Subject
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
tape.
Tom Kauffman
NIBCO, Inc
-----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
To: ADSM-L AT VM.MARIST DOT EDU
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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