Re: retention strategy

Le mercredi 08 janvier 2025 à 14:46 -0600, Rob Gerber a écrit :
> Christophe,

Hi Rob,

> I saw your correction email saying you actually do the diff on 2nd
> and 5th sunday.

Not 2nd AND 5th, but 2nd TO 5th.

> I do not think you will lose files with this first idea. Maybe you
> could have problems if you have two full backups run in a single
> month,

Yes, that's one of the problems.

>  but this would require a schedule error to occur, I think. I assume
> you have only 1 FD.

No, but the example was for one FD. I have the same config for each.
I have 6 FD.

>  MaximumVolumes="2" can only work if you have only 1 FD. Really, for
> this to work the right way you must have MaximumVolumes=X where X =
> (total FD x 2). 

And save all FD in the same pool ?
It seems to me that this will not gain me any space.

> 
> This idea below cannot work, and is dangerous. Think about it - if
> you can only have 1 full volume, you must delete your old full before
> you can make a new full. This is dangerous because you would have to
> delete your backup before you can make a new backup. 

That's what worried me.

> 
> Think of bacula volumes as tapes. Bacula started as a tape backup
> program.
> 
> 
> Bacula *is* able to add data to volumes, as I am sure you know.
> Bacula cannot remove or edit data on a volume. The only way to remove
> data is to remove the volume.

Ah !
It actually changes the whole thinking.

> I think this is because of the way tapes worked. 
> Because you want to save hard drive space, it is good to keep only a
> certain number of jobs on each volume. This means you can recycle
> volumes sooner. 

So, with Maximum Volume Jobs = 0, the volume size will continue to
grow?
So I have to find something else...
I thought I had made my life easier like that.

> 
> Have you considered compression to help use less space?

No. 
This is indeed a very good idea that I will try, but even so, it will
not completely solve my problem. I need to find the best strategy.

>  You specify compression in the fileset, in options. Compression
> tasks are done on the FD. Bacula supports GZIP, LZO, and ZSTD (ZSTD
> might be only available in newer bacula versions like 15.0.2). For my
> case I found that ZSTD gave the best mix of speed and compression.

I have bacula 15.0.2. 
What linux tool does this ZSTD compression format depend on?

> I hope this helps.

A lot.

>  Please tell me if you could not understand something.

I think I understood everything, and thank you for the clarity of the
explanations.

-- 
Christophe PEREZ


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