Replication and backups
pgoetz at mail.utexas.edu
Thu Feb 3 13:31:48 EST 2011
I'm grappling with the issue of how to either do backups or take
snapshots of a live cyrus system so that all the metadata is properly
saved; meaning that the indexes and db files match exactly the messages
in ~/cyrus/mail so that the backup or snapshot can be copied to a new
system and brought up cleanly when cyrus is started.
I recall someone on this list mentioning that they use LVM snapshots for
this purpose, but I did a little research on this, and it appears that
file system performance degrades dramatically when LVM snapshots are used.
What I'm thinking about using instead is replication with DRBD to
another server, turning off the replication periodically, making a
backup of the replicated filesystem, and then turning replication back
on. Even here, though, it seems like it would be possible turn off the
replication after a new message has been stored but before either the
indexes or the .db files are updated.
Is there any way to get around this or has the application been coded to
be "transaction safe"? This is one advantage of maildir format: the
metadata is just built right into the message filename, so the only
thing that can get lost or corrupted is the indexes, which can just be
rebuilt. Of course there's a sizable performance penalty that comes
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