Hi,
Adam Goryachev wrote on 2009-07-09 09:24:05 +1000 [Re: [BackupPC-users]
suggestion: make wakeups start at 8am]:
> Filipe Brandenburger wrote:
> > On Wed, Jul 8, 2009 at 11:39, Les Mikesell<lesmikesell AT gmail DOT com>
> > wrote:
> >>> Also, as an aside, the process should probably be renamed to
> >>> BackupPC_daily, as it makes more sense to run it during the day when
> >>> backups are not running. Isn't that right?
I don't think the name is important. It's an implementation detail. You can
change related config settings and the documentation without renaming the
binary. Does anybody care about the name "BackupPC_Admin"? People should read
documentation, and if they are about to change the time BackupPC_nightly is
run, they almost certainly have. I would guess that the origins of the name
are probably from the observation that most maintenance tasks are run during
the night, when they don't disturb anyone. Server backups are an example of
such a task, as are "daily" cron jobs.
Coincidentally, this maintenance task is not supposed to disturb backups ...
But you should keep in mind that not everyone has a dedicated backup server.
For example, I run BackupPC on an NFS/NIS/whatever-server to an external iSCSI
device. The server is idle during the night, so why not use it as BackupPC
server? The storage unit is independent; that is what seems to matter.
Obviously, I prefer BackupPC_nightly disturbing the backups rather than my
users :). I *have* seen it run during the day, and it wasn't being very subtle
about it.
If BackupPC_nightly is renamed, then why not to something that makes sense,
like BackupPC_dailyMaintenance or BackupPC_poolMaintenance or just
BackupPC_maintenance?
> >> I'm not sure you can make a general assumption about when backups are
> >> run. Most places would catch machines that are on all the time at night
> >> but there may also be a lot of desktop machines that are either started
> >> manually through the web interface or caught outside of the blackout
> >> time because they aren't available at night.
> >
> > Agreed, however some default has to be provided and the current one
> > (1am) may not be the best possible one.
Agreed. The default should be good enough for most people - particularly
unexperienced users -, disruptive for nobody, and follow the principle of
least surprise. Early morning seems reasonable. Inside the blackout window
makes sense but may be surprising.
> > As you said yourself in another thread, even though BackupPC_nightly
> > can be run while other backups are running, it is better to do so
> > while no or few backups are running so that they do not compete for
> > disk I/O
Which is why I'd argue for making BackupPC_nightly run time independent of
the WakeupSchedule. The WakeupSchedule defines possible times when backups
may be started (though they may continue or be started delayed due to
MaxBackups). Having an independent time for BackupPC_nightly where no backups
are considered makes sense, eg.
$Conf {WakeupSchedule} = [ 21, 22, 23, 0, 1, 2, 3 ];
$Conf {NightlySchedule} = [ 7.75 ];
> > Someone who uses a
> > different setup (backups during the day, at noon, etc.) will have to
> > customize these settings anyway, so they can also choose the best time
> > for BackupPC_nightly at that time.
Agreed.
> Maybe a more simple change is to add a comment to the blackout
> schedule section advising to set the nightly/daily run to during the
> blackout schedule. Also adding a comment to the daily/nightly section
> advising to schedule this for a time when you are least likely to run
> backups to improve performance. Also note that you can run it during a
> backup if desired.
I agree that the important parts are documentation changes. Everything can be
done with BackupPC as it is now, and probably the current default settings
are good enough for people who don't want to customize them. And, yes,
*better* default values may be even better for them :). Good and easily
accessible advice is best of all.
> I also agree that setting the default time inside the default backup
> window is a good idea,
"Backup window" or "blackout window"?
> that way if someone decides to change the
> default, then it is up to them to also change the other value...
>
> I also agree on renaming to daily, consider /etc/cron.daily etc, it is
> something that should be run every 24 hours, not needed to run at night.
"Daily" is not strictly a requirement. "Regularly" is (but BackupPC_regularly
is a bad name ;-). BackupPCNightlyPeriod effectively makes it traverse the
pool less often, and that's ok (hmm, what about e-mails, though?).
> As to running it at intervals less than 24 hours, I'm not sure I see
> the advantage, better to just get it to process a smaller section of
> your backup pool each day, rather than run it on the whole pool every
> x days...
I could imagine reasons to want a complete pool traversal on a particular day
rather than splitting it up equally. You might need to run full backups of all
your servers over the weekend and have no time left for a _nightly. Or you
can't run any backups on Wednesdays for some obscure reason, so that's the
ideal moment for pool maintenance. Probably not very common. If it fits into
the design, why not make it possible - someone will find a use for it -, if it
doesn't (as currently), then don't bother - nobody will miss it.
Regards,
Holger
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