Sorry to insist .. but no one on this ? is it an error in the Bacula
manual ?
thanks
On Thu, 2009-04-02 at 12:40 +0200, Julien Cigar wrote:
> Hello,
>
> In the Bacula manual I read that :
>
> "However, one must keep in mind that if your Volume Retention period is
> too short, it may prune the last valid Full backup, and hence until the
> next Full backup is done, you will not have a complete backup of your
> system, and in addition, the next Incremental or Differential backup
> will be promoted to a Full backup. As a consequence, the minimum Volume
> Retention period should be at twice the interval of your Full backups.
> This means that if you do a Full backup once a month, the minimum Volume
> retention period should be two months."
>
> I don't understand why the minimum volume retention should be at least
> twice the interval of the full backups .. ?
>
> In my configuration I do a full backup every month with a volume
> retension period of 45 days, and a daily incremental backup with a
> volume retension period of 35 days. I don't need archives on a long
> term, 1 month is enough, but I need to be able to restore a file which
> has been modified 20 days ago for example (on a daily basis, that's why
> I make an incremental backup every day).
> If I follow the Bacula manual, the minimum volume retension should be at
> least 2 months, but I don't understand why ? In my case, an incremental
> backup will never be promoted to a full, right ? For example :
>
> 1 may 0:00 am : Full backup -> volume "Full-0001"
> 1 may 8:00 pm : Incremental backup -> volume "Incr-0001"
> 2 may 8:00 pm : Incremental backup -> volume "Incr-0002"
> 3 may 8:00 pm : Incremental backup -> volume "Incr-0003"
> ...
> 31 may 8:00 pm : Incremental backup -> volume "Incr-0031"
>
> 1 june 0:00 am : Full backup -> volume "Full-0002"
> 1 june 8:00 pm : Incremental backup -> volume "Incr-0032"
> 2 june 8:00 pm : Incremental backup -> volume "Incr-0033"
> 3 june 8:00 pm : Incremental backup -> volume "Incr-0034"
> ...
> (around 15 june Incr-0001 should be recycled)
>
> 1 july 0:00 am : Full backup -> volume "Full-0001" (recycled)
>
> etc
>
> So in this configuration I will always have a valid Full backup every
> month and an incremental backup for every day of this month, and I don't
> see any situation where an incremental backup would be promoted to a
> full or that my last valid full backup would be pruned.. ?, so why
> should the minimum volume retention be at least twice the interval of
> the full backups (60 days in this example) ?
>
> Thanks for your answers,
> Julien
>
>
--
Julien Cigar
Belgian Biodiversity Platform
http://www.biodiversity.be
Université Libre de Bruxelles (ULB)
Campus de la Plaine CP 257
Bâtiment NO, Bureau 4 N4 115C (Niveau 4)
Boulevard du Triomphe, entrée ULB 2
B-1050 Bruxelles
Mail: jcigar AT ulb.ac DOT be
@biobel: http://biobel.biodiversity.be/person/show/471
Tel : 02 650 57 52
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