On Thu, 2013-12-19 at 11:02 -0500, Dan Langille wrote:
> There was a lot in the above and I couldn't parse it all
> just now.
Sorry about that; I suppose it would help if I just explicitly stated
what I really want. I have a main backup pool where all the backup jobs
write. This pool is manually copied to the archive pool using Copy jobs.
What I want is for volumes in the main pool to be recycled relatively
quickly (because space is limited), while the files are retained much
longer in the archive pool. I'd like restore attempts to automatically
figure out when the files are still available in the backup pool and use
it when possible, but get them from the archive pool if necessary.
That's what I'm working toward.
> Instead, I'll point you to something I wrote a few years ago.
> If you have questions after that, please ask again.
>
> http://dan.langille.org/2010/02/08/bacula-retention-periods/
OK, good. It's good that we're having this discussion. If I understand
any of this at all (which I may not), there are a couple of things in
there that seem not to match my experience so far. For instance, in that
document it says "you can’t restore a given file after the File
retention passed". But that's not really true. You can't restore it in
the "usual" way, by marking files, presumably because the list of
available files for marking is created using those File records that
aren't there any more. But you *can* restore those files by using a
regular expression; I've had to do this because I have lost a lot of my
File records by initially setting File Retention too low. I'm not sure
how it actually does this, but there must be some information written to
the backup volume itself that can be used to determine what files are
there. It's much slower than a database access, but I have restored
directory trees and individual files this way.
The document also says "Volumes are eligible for recycling once ALL
retention periods have passed." But that doesn't seem to be true
either; I have apparently seen Bacula recycle some volumes even though
the Job retention period has not passed. Which means, presumably, that
there are Job records in the database that point to backup files that
aren't there any more, since the Volume has been recycled.
> Perhaps the Recycling Algorithm will help:
>
> http://www.bacula.org/en/dev-manual/main/main/Automatic_Volume_Recycling.html
That does help, and I've looked at this before, but it's not always
clear (to me) exactly how it works, even after reading that.
I notice that the paragraph on Automatic Pruning says that you can't
restore files once the File records are gone, but I know that's not true
because I have done it. I suspect the documentation may be a few
versions old and I can't necessarily trust everything it says.
It also states that when volume recycling happens, "all Jobs that are
older than the VolumeRetention period will be pruned", presumably
regardless of what I set for Job Retention, which leads to some of my
confusion about what these retention periods really mean. It's even
more confusing (to me) when you throw in Copy jobs, so that the same
files may be on multiple Volumes in different pools.
--Greg
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