Andreas Piening <andreas.pien...@gmail.com> wrote on 12/22/2010 09:08:28
AM:
> One additional question: You say that the number of incremental backups
> will slow down the backup process, which makes sense to me because
> backuppc needs to iterate over all incremental backups. But which
settings
> are the "best" if I want a history that goes more than 7 days in the
past?
> For instance if I want to keep the last 14 days in the backup, is it
> enough to set "FullKeepCnt=2" and leave "FullPeriod=6.97" and
> "IncrPeriod=0.97"?
> Does "FullKeepCnt=2" still use pooling then? What I mean is: Does it
need
> twice the space as with "FullKeepCnt=1", or are there still hardlinks
used
> to address the unchanged files?
Hard links are used no matter what. The only difference between an
incremental backup and a full backup is that an incremental backup only
checks files it can detect as changed, and a full checks every one. It is
possible for a file to be changed and not detected as changed, so a full
catches this.
It has *NOTHING* to do with how much space a backup takes. Both will take
*exactly* the same amount of space (ignoring the possibility of files that
might be missed by an incremental).
If you want to be able to restore a file for each of the last 14 days, you
want a FullKeepCnt that meets your needs (at least 2, but I would
recommend something like 2,2,2--look at the documentation!), and an
IncKeepCount of something like 12. That will give you 14 days of daily
backup.
Again, read the documentation. It is extremely well done. With BackupPC,
it's easy to say something like, "I want one backup a day for 14 days, one
backup every week for 6 weeks, 6 backups every 2 weeks, and 12 backups
every 4 weeks (close enough to a month). That would give you nearly 17
months of backups, and depending on your deltas (the amount of data that
changes daily), it might take only a few tens of percent more space than a
*single* backup!
(For the record, the configuration for that is: FullPeriod=6.97 [*Very*
little reason to change this ever], IncPeriod=0.97 [Same here, too],
FullKeepCnt=8,6,12 [8 weeekly backups, 6 2-weekly backups and 12 4-weekly
backups] and IncKeepCnt=12 [12 daily incremental backups plus two of the 8
weekly full backups during that time=2 weeks of daily backups]. These are
*not* in Perl syntax, but you could enter them into the GUI as-is.)
> The more I think about it the more I understand how much "magic" must be
> going on in the backuppc backend!
Actually not that much. Much of the magic is actually in rsync; the only
real "magic" in BackupPC is that it can detect when a "new" file is
actually the same as any other "existing" file and eliminate the
duplicated space.
(Not to minimize the value of BackupPC: I love it to death. But it is
not a black box: it's actually very understandable. Still, major props
to Craig for putting everything together in an easy-to-use package!)
Timothy J. Massey
Out of the Box Solutions, Inc.
------------------------------------------------------------------------------
Learn how Oracle Real Application Clusters (RAC) One Node allows customers
to consolidate database storage, standardize their database environment, and,
should the need arise, upgrade to a full multi-node Oracle RAC database
without downtime or disruption
http://p.sf.net/sfu/oracle-sfdevnl
_______________________________________________
BackupPC-users mailing list
BackupPC-users@lists.sourceforge.net
List: https://lists.sourceforge.net/lists/listinfo/backuppc-users
Wiki: http://backuppc.wiki.sourceforge.net
Project: http://backuppc.sourceforge.net/
