Hi,
Les Mikesell wrote on 2015-04-14 09:34:35 -0500 [Re: [BackupPC-users] How to
manage disk space?]:
> On Mon, Apr 13, 2015 at 4:57 PM, <backuppc AT kosowsky DOT org> wrote:
> > Dave Sill wrote at about 15:28:49 -0400 on Monday, April 13, 2015:
> > > We've been using BackupPC for a couple years and have just encountered
> > > the problem of insufficient disk space on the server. [...]
> > >
> > > What I'd like to know is (1) where is the disk space going,
> > To store ayour backups
> >
> > > and (2) how can adjust BackupPC to use less space?
> > Save fewer backups or backup fewer machines
Jeffrey has a point here. You don't give us much detail to guess on. "A couple
dozen Linux servers" can mean just about anything.
> But more specifically, a likely problem is that you have some very
> large files like databases, log files, virtual machine images or
> mailboxes that change daily and thus are not pooled.
That is one possibility. Another would be keeping several years worth of daily
history of large mail servers. Either your history is too long (for the disk
space available), or your backups are too large, or most likely a combination
of both. Backups may be too large either by design (you need to backup too
much data) or by malfunction (you are backing up something you don't mean to
backup).
Yet other possibilities would be that BackupPC_nightly is not running, or that
linking is not working.
Then again, you might have meant to ask, "how do I find out where the disk
space is going?". I can't think of a good answer to that. BackupPC's pooling
mechanism means that if you have 100 "copies" of one file content (all linked
to one pool file by BackupPC), deleting 99 of them won't save you anything, as
long as one remains. Put differently, one host *might* seem very large in
terms of total backup size, yet share all files with other seemingly smaller
hosts. You really have to look at your source data: what are you backing up,
how often does it change, how unique is it? And you have to know your
constraints. If you *need* to keep a long history of a large amount of data,
there is nothing much you can do (except from getting more disk space). If you
don't, the easiest option is to expire old backups and see what happens - just
keep in mind that you don't get back any disk space for content still present
in more recent backups.
Reducing the size of existing backups is somewhat tricky, and reducing the
size of future backups won't gain you anything until the old backups expire.
Actually, there might be a way to shed some light. I'd probably look for large
files with a low link count (-links 2 or 3) in the pc/ tree. You need to be
aware that 'find' will take a *long* time to traverse such a large pool. It
just might be worthwhile to run a rather general 'find' command with output
redirected to a file and then filter that repeatedly to narrow down your
search, rather than running several different 'find' invocations. Or even
looking in the {c,}pool/ rather than the pc/ tree (faster, but you don't get
any file paths, just file content).
Running 'find $topdir/pc/$host/$num -type f -links -3 -ls' should give you an
approximate list of files that would actually be deleted by deleting [only]
backup $num of host $host ('-links -3' takes into account files for some
reason not linked into the pool; in theory, these *should* all be zero length,
but in case of some malfunction, they might not).
Much of that might not make any sense for your particular case, but I hope
some of it helps.
Regards,
Holger
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