Cyrus IMAP and MySQL mailboxes (Building load-balancing cluster)

[Sarah Walters]

> > > The main problem is to build a shared storage that can 
> survive server
> > > crashes, where mail will be stored.
> >
> > Use a SAN.
> First of all, such SAN must be very reliable itself. Second, it must
> support some kind of global locking mechanism, so several nodes can
> use lock to protect file from simultaneous writing. Third, Cyrus IMAP
> must lock mailboxes, so several instances on different server can work
> with one mailbox without conflicts. Whether Cyrus IMAP use locks or
> assumes that he is the only one who access mail box, I don't know. Can
> it safely access one mailbox from different servers, I don't know too.

A good commercial SAN costs a fortune, but it is very reliable. And did
you want a *cluster* or a group of servers? A cluster should operate as
if it is a single host, and thus avoid the locking issues. Have a look
at Red Hat's clustering product for an example. If our cyrus
installation was going to be clustered, RH cluster with a SAN backend is
what we would do.

Regards,
Sarah Walters