John Rouillard <rouilj-backu...@renesys.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
Out of the Box Solutions, Inc.
Creative IT Solutions Made Simple!
http://www.OutOfTheBoxSolutions.com
tmas...@obscorp.com
22108 Harper Ave.
St. Clair Shores, MI 48080
Office: (800)750-4OBS (4627)
Cell: (586)945-8796
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