[OpenAFS] Failover

Dave Broudy dave@broudy.net
Sat, 31 Dec 2005 19:08:43 -0700

Jeffrey Hutzelman wrote:

> I very much recommend against trying to store mail in AFS.  There is 
> no gain to be had in reliability, scalability, or performance, and 
> there are any number of potential problems.  If what you're trying to 
> accomplish is to get those features in a distributed mail server 
> system, I suggest looking at http://asg.web.cmu.edu/cyrus/

I too am contemplating storing mail in AFS. Reading through the cyrus 
site, it seems to have it's own set of compromises. But regarding 
availability, the documentation of the Cyrus IMAP Aggregator, Secion 4.3 
Summary of Benefits (http://asg.web.cmu.edu/cyrus/ag.html) seems to 
contradict what you're saying. It's "availability" simply guarantees 
that your whole mail system won't go down, not that at individual 
mailbox will always be availble. This seems to me to be pretty much the 
same guarantee that AFS provides by having a RW user volumes on a couple 
of different file servers.

I'm admittedly a novice with AFS and cyrus (currently using courier), 
but it seems to me like the best approach might be to tightly couple 
(same server or same LAN) a cyrus backend's mailboxes, the mail delivery 
(LTMP) and the AFS volumes that make up the storage. Then you know that 
you won't have two IMAP servers fighting for the same directory, but you 
still have the apperence of a unified server the cyrus provides. You 
could also then have some other IMAP server take over for a failed IMAP 
server by some external means.

Dave Broudy
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