Hi,
I get some diagnostics when reading this with 'use warnings "wrong_numbers"' ...
backu...@kosowsky.org wrote on 2013-11-01 12:18:17 -0400 [Re: [BackupPC-users]
Disk space used far higher than reported pool?size]:
> Craig O'Brien wrote at about 10:11:07 -0400 on Friday, November 1, 2013:
> > >And this would explain why the elements are not being linked properly to
> > the pool -- though I would have thought the more likely result would be a
> > duplicate pool entry than an unlinked pool entry...
> >
> > >It might be interesting to look for pool chains with the same
> (uncompressed)
> > content and with links < HardLinkMax (typically 31999) to see if pool
this one looks correct. 31999. Unless of course you've changed it in config.pl
because your FS requirements differ.
> > entries are being unnecessarily duplicated.
> >
> > >Try: (cd /var/lib/BackupPC/cpool; find . -type f -links -3198 -name "*_*"
> -exec
This one doesn't.
> > md5sum {} \;) | sort | uniq -d -w32
> >
> > > Note this will find if there are any unnecessarily duplicated pool chains
> > (beyond the base one). Note to keep it fast and simple I am
> > > skipping the elements without a suffix... with the assumption being that
> > if there are duplicated elements then there will probably be
> > > whole chains of them...
> >
>
> I added some more bash-foo so that the following should find *any* and *all*
> unnecessary pool dups...
>
> (cd /var/lib/BackupPC/cpool; find . -name "*_0" | sed "s/_0$//" | (IFS=$'\n';
> while read FILE; do find "${FILE}"* -links -3199 -exec md5sum {} \; | sort |
> uniq -D -w32 ; done))
Nor does this one (the 3199 again). While it will find chain members with
less links than apparently necessary, it won't find all of them - only those
with *far* too small link number. That might be sufficient, depending on what
we're looking for. You probably wouldn't have chosen the (arbitrary) value
"3199", though, if you hadn't in fact meant "31999" ;-). And you wouldn't be
saying "*any* and *all*" if you were meaning "some".
I'd like to point out three things:
1.) unnecessary duplication *within* the pool is not the problem we are
looking for,
2.) if it were a problem, then because a duplicate was created way ahead of
time and repeatedly, not because the overflow happens at 31950 instead of
31999,
3.) finding "unnecessary duplicates" can have a normal explanation: if at some
point you had more than 31999 copies of one file (content) in your
backups, BackupPC would have created a pool duplicate. Some of the backups
linking to the first copy would have expired over time, leaving behind a
link count < 31999. Further rsync backups would tend to link to the second
copy, at least for unchanging existing files (in full backups). In other
cases, the first copy might be reused, but there's no guarantee the link
count would be exactly 31999 (though it would probably tend to be).
Having so many copies of identical file content in your backups would tend
to happen for small files rather than huge ones, I would expect, and it
doesn't seem to be very common anyway (in my pools, I find exactly one file
with a link count of 60673 (XFS) and a total of five with more than 10000
links, the largest having 103 bytes (compressed)).
Regards,
Holger
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