High availability ... again

[Etienne Goyer]

Greeting fellows,

I know this discussion crop up regularly, but I have checked the list 
archive and the WiKi already and did not really found the answer I am 
looking for.   Also, an update once in a while might be a good thing.

I have been asked to consider how to build an high-availability Cyrus 
installation.  This is a small installation (~200 accounts ... peanuts), 
so scalability is not really a concern.  In this regard, a Murder is not 
really appropriate.

The platform would be Linux.  We already have the fail-over stuff 
figured out with heartbeat and friends, so that part is covered.

 From what I can see, I would have two possibilities to make a hot spare 
Cyrus IMAP daemon : replication, or cluster filesystem/block device 
(drdb, GFS, etc).

Regarding IMAP replication, I have not found much but the work of David 
Carter at http://www-uxsup.csx.cam.ac.uk/~dpc22/cyrus/replication.html 
seem interesting.  As far as I can tell, source to this implementation 
and current status are not available.  Does somebody on the list use 
this solution or a similar one and could comment and the practicality of 
it ?  Perhap M. Carter (if you read the list) could give us a status 
update for his particuliar project ?

Regarding cluster filesystem, I am just starting to look around and 
would like to know about success story.  So far, drdb and GFS look 
somewhat promising.  The WiKi mention that the filesystem need to 
support file locking and mmap(), so I guess this is something to be on 
the lookout for.  Does anybody use clustered filesystem for their Cyrus 
mailstore ?  I am particularly interested to know if you use drdb or 
GFS, and your overall feeling about their suitability for this task.

Thanks for your insight.  I know my questions are somewhat vague, but I 
would welcome your experience with HA and Cyrus or any pointer you may 
have on the subject.

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