Date: Wed, 16 Sep 2009 14:49:28 +0100 From: Matthew Seaman <m.seaman@infracaninophile.co.uk> To: Steve Bertrand <steve@ibctech.ca> Cc: "questions@freebsd.org" <questions@freebsd.org> Subject: Re: New mail server setup Message-ID: <4AB0ECE8.2080905@infracaninophile.co.uk> In-Reply-To: <4AB0E97B.4060606@ibctech.ca> References: <4AB0584D.3050206@eagle.ca> <4AB0844B.5080804@infracaninophile.co.uk> <4AB0E97B.4060606@ibctech.ca>
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Steve Bertrand wrote:
> What I don't have, and have always wondered about, is live redundancy
> for the IMAP/POP services.
>
> I know that this would be a challenge to some degree considering the
> high volume of data changes.
>
> Perhaps a carp(4) setup between a couple of MDA's, where when the
> primary is up, a constant rsync pushes the data to the backup. Or
> perhaps a combination of rsync for manual changes, and a method to have
> the primary write the emails to a local disk, and a network disk
> simultaneously?
>
> If anyone has a setup that has redundancy for their IMAP/POP services,
> and a method to keep the changing data relatively up-to-date, I'd love
> to hear about it.
Now, that is a different kettle of fish. This is a job for cyrus imap.
I suggest googling for 'cyrus murder' -- this is almost, but not quite,
a fully resilient mail store / IMAP system. Your mail store is divided
into frontend IMAP protocol servers which handle user auth etc. and back-end
mail stores. The protocol layer servers are fully resilient and you can
fail over a user session at will, but the mailstores don't quite get there:
mail is replicated across different stores, but actions modifying the mail
store are not transactional across all the mail stores. Or in other words,
you can lose a small amount of data if one of the mail stores goes bang at
precisely the wrong moment. Even so, it will do better at keeping multiple
copies of a mailstore in synch than any locally scripted rsync setup.
Cheers,
Matthew
--
Dr Matthew J Seaman MA, D.Phil. Flat 3
7 Priory Courtyard
PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate
Kent, CT11 9PW, UK
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