I've been using BackupPC for ages and have been anticipating this
feature very much. However, my real-world results from BackupPC 3.0.0
don't really show this behaviour. My results look as follows:
15 full yes 0 21/4 02:00 43.5
19 incr no 1 25/4 02:00 6.6
20 incr no 1 26/4 02:00 7.5
21 incr no 1 27/4 02:00 8.1
22 full yes 0 28/4 02:00 62.3
23 incr no 1 29/4 02:00 6.4
24 incr no 1 30/4 02:00 9.1
25 incr no 1 1/5 02:00 8.5
I unfortunately do NOT see the 2nd full (backup 22 above) appearing to
be incremental to 21 before it. This is definitely an rsync backup and
this is also definitely BackupPC 3.0.0. Is there perhaps something
really stupid that I am missing ?
Stefan
Craig Barratt wrote:
> This is a new feature in 3.0.0: the reference backup for an
> rsync full is the latest backup (of any kind). In 2.x only
> the last full was used as the reference for any rsync backups
> (whether incremental or full). The only penalty in doing this
> is that it takes more server disk accesses to create the "merged"
> last backup (ie: the full plus potentially one even several
> incrementals if $Conf{IncrLevels} is used).
>
> Actually, in looking at the code I realize that in 3.0.0 the
> reference backup for an rsync incremental is the last backup
> of the next lower level (this is the same definition used for
> tar and smb backups). With the default $Conf{IncrLevels} of 1,
> that means each incremental always uses the last full as the
> reference.
>
> So these posted results make sense:
>
> > >> For instance, as a test...
> > >>
> > >> 0 full 10min
> > >> Add a bunch of files.
> > >> 1 incr 6min
> > >> 2 incr 6min
> > >> 3 incr 6min
> > >> 4 full 0.1min
>
> Each incremental uses the #0 full as a reference, so they each
> transfer the same amount of data and take the same time. The
> full in 3.0.0 uses #3 (ie: #3 merged with #0) as the reference,
> and it doesn't need to transfer nearly as much data. In 2.x
> I would expect the #4 full to also take 6 min.
>
> Unless I'm forgetting a good reason why I did it that way, for
> rsync I should make the reference backup the most recent backup
> in all cases - both full and incremental. It's a pretty simple
> change - I'll add it to the todo list for 3.1.0. The logic is
> correct as is for smb and tar: the reference backup for an
> incremental always is the backup of the next lower level.
>
> Craig
>
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