Re: [BackupPC-users] overlapping BackupPC_nightlys

[Tino S. <bac...@ti...>]

On Thu, Apr 17, 2008 at 03:41:53PM -0400, Tony Schreiner wrote:

> >> On one of my BackupPC setups, I back a lot of data. On occasion
> >> things run for more than 24 hours and I start getting
> >>
> >> .... Botch on admin job for  admin : already in use!!
> >>
> >> messages in the log file. I'm guessing that this means that a
> >> BackupPC_nightly has been queued when there is already one running.
> >>
> >> My question is, eventually they all run to completion, but is there
> >> any value in queueing one up when another is already running? Does
> >> running one after the other make any sense?
> >
> > Just set $Conf{BackupPCNightlyPeriod} = 2; Or 4 or whatever. That way,
> > BackupPC_nightly will do only a part of the pool each run.
> >
> > Bye,
> >
> > Tino, having that setting at 4.
> 
> Sorry, I replied first to Tino; here it is again to the list:
> 
> 
> I can do that, yes, But the BackupPC_nightly actually do complete,  
> even when 3 or 4 get run in succession.
> 
> I'm just wondering if the 2nd and 3rd time BackupPC_nightly -m 0 127  
> runs in a row actually does anything.

There are two settings for BackupPC_nightly: BackupPCNightlyPeriod and
MaxBackupPCNightlyJobs. My experience is that it makes no sense to set
MaxBackupPCNightlyJobs to anything higher than 1 since the whole job is
I/O-bound anyway and doing almost no CPU-intensive operations.

The BackupPC_nightly job should only run once a day, processing a part
of the pool (depending on the period setting). The next day, the next
part is processed etc. It skims through the pool and looks for files
which are no longer in use by any backup.

The whole process works roughly like this:
- backups are done by BackuPC_dump on per-client basis, no explicit
  pooling involved yet (apart from full backups where existing/unaltered
  files are linked into the new backup from last full, so link count in
  the pool increases too)
- BackupPC_link traverses completed backups and links new files to the
  pool (so the new file has link count 2)
- when a backup starts, old backups get expired and are moved to the 
  trash directory without further processing
- BackupPC_trashClean simply removes everything in the trash
  periodically -> link count on some files in the pool decreases
- BackupPC_nightly skims through the pool and removes files with link
  count 1 since they are not used by any backup any more

HTH,

Tino.

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