dovecot - Feb 2010 - Dovecot design-question

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?

- Is it possible to activate loadbalancing for SMTP in this environment
if dovecot index-files are held locally on each machine (POP/IMAP is
directed only to one of the two servers?)

Any comments welcome :-)
Werner

Hi,
> - 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?)
like mentioned on the website, but "would it be possible without nasty
errors" ?
> - If we think of a "active/passive" setup: dovecot index-files
locally
> or on the nfs-share?
what's the better approach here?

thank you,
Werner

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