This can minimize the risk, but if you don't need the corrupted file
actually, you can't detect that it is corrupted.
The corrupted file will be copied to a newer backup folder.
If you delete the old backups due to rotation, at any time the backup
is worthless because it only contains the corrupted copy.
So some mechanism is needed to detect corrupted files before copying
to the backup.
Best regards
Christian
Am 24.05.2009 um 16:04 schrieb Mac User FR:
A simple way to prevent this is to store the backup with a rotating
system and hard-linking files.
You can do it with rsync --link-dest=DIR option and a post-exec
script that moves the backup dir to something like backup-200905241335
In this way if the file got corrupted it won't be hard-linked and
you will have a safe copy from a previous backup. Hard-linking an
unchanged dir takes very few place.
Best regards,
Vitorio
Le 24 mai 09 à 15:05, Christian Hecht a écrit :
This will safe you if your file is corrupted on the backup side.
Rsync will copy it then again from the source because the checksum
is different and everything is okay.
But imagine the file is corrupted on the source side. Then rsync
will copy the corrupted file again and if you delete older backups,
at any time your backup is corrupted too.
Someone pointed me to this case a few weeks ago, so i started
thinking how to avoid this.
I will try to write a tool which stores the rsync checksums ore
generate own checksums for each source file.
Then, at any time the stored checksums can be compared with the
source files.
Best regards
Christian
Am 22.05.2009 um 16:22 schrieb Daniel Carrera:
Matthias Schniedermeyer wrote:
Exactly.
But you can (periodically) add "-c", then rsync while checksum
the whole content of all files.
Thanks. I'll add a -c for the Saturday backup.
But IF you have (or suspect) such type of corrution, you have
have an even greater problem: Your hardware is crap.
Yeah. I hope I don't have that particular problem. But I want to
be prepared if it happens.
Daniel.
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