Hi list,
I think I found a bug with the pc/backups "state" files, or with file
locking or something like that, not sure what the correct terminology
is. I'm running BackupPC-3.2.1-7.el6.x86_64 on CentOS release 6.2
(Final) 64bit.
Here's what happened:
1. Every now and then, like every 4 or 5 months, my backup server
crashes, out of memory (not enough RAM) or something like that. When
it's not responding anymore, like it was the case today, when no login
on the console is possible anymore and CTRL+ALT+DEL won't work, I have
to hard reboot it.
2. My storage is on a QNAP NAS via iSCSI and it's mounted as
/var/lib/BackupPC. When the server comes back online after a reboot,
everything is fine, all the files are there... almost... because pretty
much the most important files when it comes to BackupPC are *sometimes*
zeroed, namely the pc/backuppc files in each hosts' directory
(/var/lib/BackupPC/pc/hostname/backups).
3. So in this particular case, after the reboot, BackupPC reported under
Host Summary: 6 hosts that have been backed up, 21 hosts with no
backups. Wait... it should say 27 hosts have been backed up. So I had a
look at the pc/ directories for all the hosts and the 'backups' file had
0 bytes for those 21 hosts.
4. Fortunately, for most hosts, a backups.old file existed which was
just a few hours older than the backups file, so I copied backups.old to
backups for each host and the backups for 23 hosts now show up again in
the web frontend. Not sure about any inconsistencies but I'm guessing it
doesn't matter or it will figure it out by itself. :)
5. Except for 4 hosts where the backups.old file was also 0 bytes. So
these backups are lost, although the actual backed up data is still
there of course, but I won't bother with recreating the 'backups' file
by hand or something like that, it's not that important, and in 1-2 days
I'll have a good, useable backup again. It will just start from scratch
for those 4 hosts.
6. I "lost" these 4 hosts because I'm not backing up the 'backups'
files. :P Well, this is the second time now this has happened. I would
say it happens in about 33% of the cases where I have to hard reboot the
server. Please note: all other files are there! Just the 'backups' state
files are 0 bytes, well, for most hosts.
7. My mount options are (mount -v output): /dev/mapper/data-rz--nas01 on
/var/lib/BackupPC type xfs (rw,_netdev)
I'm speculating BackupPC needs a better "locking" feature of some sorts?
Or another mechanism that this can't happen again. Or maybe I need to
upgrade to the latest version?
Thank you!
Markus
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