High availability mail server options

[David Hollis]

On Tue, 2005-10-04 at 06:13 -0700, Craig White wrote:
> On Tue, 2005-10-04 at 08:03 -0400, David Hollis wrote:
> > For my company, I've setup a mail/groupware environment that uses
> > Postfix, OpenLDAP, Postgres, Apache, etc and am now looking at ways to
> > make it a more redundant arrangement.  All of the components have
> > methods to help me with the lone exception of the backend mail storage
> > for the end users.  Ultimately, I am wanting to have systems at
> > different geographic locations, not even on the same network, ideally
> > with users able to access any of them at anytime and be able to do their
> > thing.  The users mail storage is in Maildir format which seems like it
> > will help any replication type scenario.   I can't just NFS mount the
> > mail directories, because then my NFS server becomes my single point of
> > failure.  Do things like GFS work to handle this?  If so, do they
> > operate across slow links (not talking dial-up here, but general
> > Internet cable/DSL type links)
> > 
> > If it helps, our total mail volume is not that tremendous so completely
> > instantaneous replication isn't totally necessary, but I would want
> > fairly quick convergence (say 30 minutes or less).
> > 
> ----
> I think you will find that most IMAP servers aren't real keen on using
> an NFS storage backend anyway. I can't conceive how maildir data store
> has anything to do with replication. GFS would work - cyrus-imapd also
> offers murder for a multi-server approach. Backup is always a bear on
> these things that you have to consider.
> 

Where I see Maildir helping is that the messages are stored in
individual files instead of very large mbox files.  Once a message is
replicated, most of the time it won't need to be replicated again unless
something changes on it (marked as read, urgent or whatever).   It would
seem that replicating 1GB worth of small files with a large number of
the files being static would be easier than a 1GB single file that is
constantly changed.  

-- 
David Hollis <dhollis at davehollis.com>
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