[Dovecot] Dovecot "sleep" for short snapshots

[Jack Bates]

On 12/15/2012 1:52 AM, Peer Heinlein wrote:
>
> Making consistent backups from Dovecot with mdbox requires a snapshoted
> filesystem with (at least) a short Downtime for Dovecot.
>
> I'd like to avoid killing several thenthousand IMAP-sessions for 60
> seconds. Users don't like that... And the admin dislakes that too...
>
>

Are you sure it is necessary? I'm not very familiar with mdbox, but 
given the rundown on the wiki, it looks as though it should be very 
resilient to snapshots even mid-write. With fs-freeze and the nature of 
bulk writes, I suspect it should be fine. At worst, it might need to 
regain sanity off the backup indexes. Since file rewrites are done 
during the purge script, I'd definitely not do snapshots during the purge.

The last I checked, the fs-freeze api isn't complete. It would make more 
sense for dovecot to work with that structure once it is completed 
(allowing fs-freeze to inform dovecot that the fs will be 
freezing/unfreezing).

Jack