Replication and failover

[Rob Mueller]

> Attached is our operation group's notes on the subject.  It makes
> reference to the tool we use to manage the OS of the machines
> (radmind), but it should be pretty clear what they are talking about
> without any radmind knowledge.

As an FYI, we have a similar procedure to this, the main differences are:

1. We don't change the DNS. Instead we give each machine a primary IP 
address, but we also create IP addresses for "cyrusXmaster" and 
"cyrusXreplica" names(where X is numbers for each machine). When we swap 
roles, we rebind the different IPs to the particular machines and send ARPs 
to clear the router table, rather than changing the DNS. This means you can 
always access the master as "cyrusXmaster" from every machine without having 
to worry about DNS getting out of sync.
2. Every machine has cyrus-master.conf, cyrus-replica.conf, 
imapd-master.conf and imapd-replica.conf. We just symlink cyrus.conf and 
imapd.conf to the appropriate file depending on what mode the machine is 
currently in

Rob