[Dovecot] Dovecot design-question

[Ed W]

On 01/02/2010 10:05, Werner wrote:
> Hi everybody,
>
> we're currently in the process of drafting our new mailserver-setup.
> Instead of a single-server-setup we'd like to have two equal servers
> behind a loadbalancer like LVS and shared mailhomes on NFS.
>
> We'd like to use dovecot for POP/IMAP, dovecot-deliver as LDA.
>
> - It's probably the best idea to direct SMTP and POP/IMAP always to
> the same server behind the loadbalancer (because dovecot-deliver is
> used which updates indexes?)
>
> - If we think of a "active/passive" setup: dovecot index-files locally
> or on the nfs-share?
>
>    

At least one other user on the list had success using Dovecot proxy and 
a "backend servers are the frontend servers" setup.  Basically the user 
comes into a random frontend server, the dovecot proxy has a 50:50 
chance to discover they are already on the right machine and gets out of 
the way, otherwise it proxy's the connection to the other machine.

I guess this will waste 25% internal bandwidth on average (external b/w 
should remain the same).  Apparently cpu requirements are very low for 
proxying and additional memory requirements can be measured, but may be 
satisfactory

If one server fails then you have to update the loadbalancer to redirect 
only to the working server AND update the proxy not to try and send 
users to the other machine.  Depending how you configure things this 
extra step can be done very easily though.

Good luck

Ed W