Re: Aggressively prune (and truncate) file volumes on Progressive backups...

Bill Arlofski via Bacula-users <[email protected]> Wed, 02 Oct 2024 21:20:55 +0000
Newsgroups	gmane.comp.bacula.user
Message-ID	<[email protected]>
On 10/2/24 10:00 AM, Marco Gaiarin wrote:
> Mandi! Gary R. Schmidt
>    In chel di` si favelave...
> 
>> RTFM again, it took me about three goes to understand it - and I've been
>> doing backups since 9-track tape drives were vertical!
> 
> Mmmmhhhh... i've found references to scratch pool but really i've nefer
> understood; if i look in docs i found a rather laconic:
> 
> 	https://www.bacula.org/9.4.x-manuals/en/main/Configuring_Director.html#SECTION0020161000000000000000
> 
> seems there's no whitepaper on scratch pools...
> 
> 
> So, RTFM where?! ;-)

Hello Marco,

Typically Scratch pools are not too useful for disk volumes.

The idea behind a Scratch pool is the following:

Let's say you have two pools: "Full", and "Inc"

If you do not have a "ScratchPool" to pull from, and a RecyclePool to send recycled volumes back into, then tapes created in 
the Inc pool (for example) will never be available to be used in the Full pool - even if they are all past their
 retention 
and have all been pruned and recycled. They are doomed to this Inc pool forever. :)

So, you could have job(s) writing to the Full pool all waiting on media which is technically available (pruned and living in 
the Inc pool), but not available for use by jobs in the Full pool.

So, what you do is set "ScratchPool = ScratchPoolName" and "RecyclePool = ScratchPoolName" in your Full and Inc Pools. Then, 
make sure to enable Recycling (Recycle = yes) in the pools.

Then, when tapes are labeled (using the 'label barcodes' command in bconsole), you specify the ScratchPoolName as the initial 
pool where they will be created and then Bacula will pull from the Scratch pool when a tape is needed, and put it back there 
when it is recycled so that the tape is then free to move between the Full and Inc pool as it becomes available, and as 
necessary by Bacula's needs.


I do have a use case for ScratchPool and RecyclePool settings in Disk volume pools... In my case I use
 Josh Fisher's 
'vchanger' so each of my xTB removable drives can have 10 file volumes in either my Inc or Full offsite pools. Disk volumes 
on each physical/removable xTB disk can freely move as described above so I never run into a situation where the whole 
physical disk is full of 10GB volumes in the full pool when Inc pool volumes are needed for a job and vice versa.


Note: A pool named "Scratch" is treated a bit special by Bacula. If no `ScratchPool` is specified in a pool, Bacula will look 
for volumes with the correct MediaType in this pool.   But, you can name your scratch pools anything you like and never use 
this specific one.

For example, If an SD manages more than one tape library, you can have a set of pools for Lib1:
  - Lib1_Scratch, Lib1_Full, Lib1_Inc

And then a set of pools for Lib2:
  - Lib2_Scratch, Lib2_Full, Lib2_Inc


Hope this helps,
Bill

--
Bill Arlofski
[email protected]

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