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Re: [BackupPC-users] backuppc slow rsync speeds
2012-09-18 10:19:12
John Rouillard <rouilj-backuppc AT renesys DOT com> wrote
on 09/17/2012 01:30:36 PM:
> AFAIK this is not correct. If checksum caching is enabled, backuppc
> will check the cached checksums against the actual file contents based
> on the setting of the:
>
> $Conf{RsyncCsumCacheVerifyProb} = 0.10;
Yeah, I probably should have mentioned that. I
knew it was there, but I'd rather have that set to 1.00 than 0.10... :)
> Also even with checksums turned off, you could have an older copy
of
> the file in the pool go bad and you wouldn't know it till you tried
to
> restore it, so having checksum off doesn't protect you from bad data
> in the pool except for the most recently used files.
This is perfectly valid. However, I'm less worried
about data that has multiple copies (older != newer) than I am about important
data (or data that *becomes* important) but hasn't been modified in enough
time so that there is only a single copy of it stored--the same copy in
each of, say, six months of backups.
I've had that happen in *more* than one case. (Another
related case is a "vitally important" file that disappeared at
least six months ago but *must* be brought back...)
Both of these can be dealt with by duplicate externally
managed archives, etc. but this is exponentially more annoying to deal
with than BackupPC. If I can solve a problem there, I would prefer
to. Monolithic 500GB tar files (aka BackupPC archvies) are not user-friendly.
> (We also won't discuss having corruption in putting
the current bits
> on disks that trashes the curent backup copy. Which frankly there
is
> very little short of zfs/btrfs type filesystem that can provide some
> measure of protection/detection.)
Or, like I said, multiple externally managed archives
using separate and redundant medium. I have that, too. It's
just a big pain to use, that I would rather do nearly anything else than
depend on it! :)
Unfortunately, none of this gets us closer to the
source of the terrible performance we're seeing... :)
Timothy J. Massey
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