[Dovecot] Replication plans

[Francisco Reyes]

Troy Benjegerdes writes:

> But that's currently not *really* replicated. The real question I guess
> is why not use a cluster/distributed/san filesystem like AFS, GFS,

Because those distribute filesystems may be more difficult to setup, more 
difficult to maintain and may be less portable than a dovecot solution.

For example Gluster sounds really like a great distributed filesystem, but 
it currently does not work in FreeBSD.

If the company I work for wanted to use Gluster we would need to either 
learn Linux or hire someone to setup  and maintain the linux boxes for us.

> I'd suggest that multi-master replication be implemented on a
> per-mailbox basis

I suggest we forget about multi-master for now. :-)
Some of us would rather see something sooner rather than later.

> I like the idea of dovecot having a built-in proxy/redirect ability so a
> cluster can be done with plain old round-robin DNS.

Round-robin DNS is ok for a small setup, but not good enough for larger 
setups.

> most cases, if there's a dead server in the round-robin DNS pool, most
> clients will retry automatically, or the user will get an error


And you will get dozens of calls of users asking what is going on, and why 
are things slow, etc. etc... and there goes half your morning/afternoon.

Even with a small TTL outlook is so flaky that often times after a brief 
problem outlook needs to be rebooted.

Where I work we may have a 15 minute problem that takes us 2 hours of calls 
to handle.. in large part because of outlook or people just wanted to know 
what happened.. and expecting a call back with an explanation.

Failover needs to be seemless and without error.
Either have a proxy from dovecot in front or a load balancer.