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On Wed, 13 Feb 2013, Reindl Harald wrote:
Thanks, if I did:
rsync --force --delete-after -tPrlHpogEAXz /folder/ /backups/newmailstore/
could I then tar up the newmailstore folder with something like tar zcf without messing anything up?
keep in mind, that the backup of the Maildir with rsync is no 100% consistent snapshot, because of the filename renames; otherwise: yes
who would rename them and why?
"/folder/" would be a Maildir on a production mail server. If rsync runs (without help from other funtionality, such as LVM or ZFS snapshots) and at the same time someone accesses the Maildir and:
a) "see"s a message, which lets Dovecot rename the message file from ***/new/ to ***/cur
b) tags a message with a keyword, which lets Dovecot rename the file to have some lower-case letter
c) untags a keyword -> remove that letter from the filename
d) changes Deleted, Read, Answered status --> add/remove an upper-case letter from filename
rsync might have cached a message with an old filename no longer physically present on disk. You will see a "XYZ vanished" message and that particular message is not backuped, but removed from backup. Some scripts use rsync in a loop in assumption, that no Maildir is accessed that often, that you get a clean run of rsync eventually.
Maybe, if you tag a message with a new keyword, rsync already copied dovecot-keywords without the new keyword, but copy the message, when its filename has the keyword-letter.
In fact, if I want to make 100% sure I get an exact copy, I do this:
rsync /from /to rsync /from /to mv /from /from_locked sleep 1 rsync /from_locked /to mv /from_locked /from
"/from" is the base directory of the Maildir. In my environment that causes tempfails on delivery and internal server errors on IMAP/POP3 access. But the time between the two mv's is very small, because the main differences are handled with the first two rsync's. As you seen, I copy one user after another, which breaks hardlinks between users, but keeps memory footprint of rsync low and as well as the downtime.
I do make my usual daily backups without the loop and the mv's, because it is very seldom I get the "vanished" messages. I suppose, because the script runs two hours after midnight.
Steffen Kaiser -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux)
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