ADSM-L

Re: [ADSM-L] Collocaton by group

2011-11-30 14:20:08
Subject: Re: [ADSM-L] Collocaton by group
From: "Allen S. Rout" <asr AT UFL DOT EDU>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Wed, 30 Nov 2011 14:16:32 -0500
On 11/30/2011 12:31 PM, Hans Christian Riksheim wrote:


I have 1 node where I want collocation, the rest not. [...]  I think
I just go for collocate=no.

Unless you have pretty specific reasons to mush the rest of them
together, I'd call this a poor configuration.

How many tapes do you have? Now envision _all_ of them being mounted
for any restore, even a relatively small one.  That's the end state of
colloc=no: to a first approximation, every node, every filespace,
every directory, is smeared across a maximum number of tapes, with no
tendency to re-group data which is predictably related.

Collocation is about paying, in unused tape space, for efficient
restores;  I'd suggest you view that as a bargain, not a burden.

I recommend you leave colloc on, and rather than worry about
rejiggering collocgroups every time you make a new node, rejigger them
when your scratch count gets "low", whatever that means in your
environment.  Several folks here (including me) have posted the
scripts they use to do their analysis and modifications, so it need
not be a major time sink.


- Allen S. Rout

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