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Re: [Bacula-devel] Multiple storage daemons - multiple scratch pools?

On Thu, Dec 11, 2008 at 01:29:48PM +0100, Eric Bollengier wrote:
> Le Thursday 11 December 2008 12:34:42 Graham Keeling, vous avez écrit :
> > Since sending my original patch, we came up with a slightly different idea
> > that required much less change to the code, and is therefore likely to be
> > safer. I am currently using this new idea instead of the original one.
> >
> > It goes like this:
> > If Pool A needs a volume and has a RecyclePoolId is pointing to a Pool B
> > that is of type 'Scratch', then Pool A can take a volume from Pool B.
> > If it was unable to do that, it falls back to trying to take a volume from
> > the pool named 'Scratch'.
> > When it is autopruning, it can cause volumes with a RecyclePoolId pointing
> > to the same Scratch Pool as the current Pool's RecyclePoolId to be
> > pruned/purged and moved into that Scratch Pool.
> I'm not sure that it is a good idea, RecyclePool and ScratchPool are two 
> different things. We can see that like a cycle.

Note that Graham said the suggested new behaviour is only triggered if you
define the pool targetted by RecyclePool as having Pool Type = Scratch.
If you leave it as an ordinary Backup pool, as it would be in your example,
the behaviour is the same as before.

The existing behaviour for the recommended RecyclePool = Scratch set-up
is also preserved by this change.  At the moment, the scratch pool is
magic because it is named 'Scratch', but after the change, it behaves
in this special way because it is Pool Type = Scratch, which seems rather
more obvious.

In fact, if we could be sure people followed the documentation, we
could remove any special handling of the pool name 'Scratch' entirely.
However, this would change the behaviour of existing configurations
that use RecyclePool = Scratch but declare the Scratch pool to have
Pool Type = Backup.  Although that's not the documented way to do it,
the Pool Type doesn't seem to matter, so people could be doing that wrong
and not notice.  Hence Graham's change keeps the special behaviour of
the name 'Scratch' as a fall-back.

Robin O'Leary.
email: robin@xxxxxxxxxxxx    Equiinet Ltd., Edison Road, Dorcan,
Tel.:  +44 1793 603708       Swindon, SN3 5JX, U.K.  51.5558N,1.7286W

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