Bacula-users

Re: [Bacula-users] Job, File, Volume Retention?

2010-10-25 15:33:56
Subject: Re: [Bacula-users] Job, File, Volume Retention?
From: Craig Miskell <craig.miskell AT opus.co DOT nz>
To: bacula-users <bacula-users AT lists.sourceforge DOT net>
Date: Tue, 26 Oct 2010 08:30:23 +1300
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Mingus Dew wrote:
> All,
>      I recall reading about this long ago, when I read the manual like a
> book. I'm having a hard time finding the information now,
> 
> I have configured Job and File Retention periods in the Job Definitions
> and then Volume Retention periods in the Pool Definitions
> 
> Job Retention = 30d
> File Retention = 30d
> 
> Volume Retention = 14d
> 
> Which retention period will be the one implemented, or will this produce
> some resultant Retention that I'm not aware of?
Hi,
        Here's something I wrote for our internal documentation on retention 
periods
that might help explain things.  It's a distillation of what's in the official
documentation, in a format that made more sense to my little brain.  I believe
it to be correct, but I'm open to corrections of fact:

There are three retention periods:
   1. File Retention
   2. Job Retention
   3. Volume Retention

The most important thing to know is that the first two (File and Job) are about
database records and are configured for a Client, and the last (Volume) is about
tape recycling and is configured for a Pool.

*File Retention*
File retention is about when the File records are purged from the database. File
records are detailed information about the files (name, timestamps, attributes,
directory structure etc) that are in a given backup. They are required if you
want to use bconsole (or some other interface) to browse/select files in a
backup, rather than just restore an entire backup job.  Once they have been
purged, they can be recovered by rescanning the tape, but this obviously takes
some time (typically hours). Deciding what value this should be is a trade-off
between the size of the bacula database and how long it will take to rescan.
Considerations include how often you restore files from rather old backups, and
how long users are willing/able to wait for those restores to occur. This will
be very locally specific.

*Job Retention*

Job retention is also about the database records, but refers to just the job
meta data (relatively small). All the File records refer to a Job, so if the Job
record is purged, the File records for that job will be purged also. The reverse
is not true (deleting File records doesn't delete Job records). This means that
if your Job Retention is smaller than your File Retention, the File Retention is
irrelevant.

*Volume Retention*

Volume Retention is utterly distinct and is to do with when tapes in a pool can
be recycled for re-use. That's why it's set in Pools rather than Clients (it is
meaningless in a Client configuration)

Hope that helps you and others.

- --
Craig Miskell
Senior Systems Administrator
Opus International Consultants
Phone: +64 4 471 7209
 "Unmoved. Like someone who's taken a laxative but it hasn't worked yet.
 I get this feeling quite often when dealing with NT."
        -- Tanuki
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