Hi Richard,
You can use one or more instances of Dovecot on the same machine, as you can see here (http://wiki2.dovecot.org/RunningDovecot) "Running Multiple Invocations of Dovecot".
The problem with DNS round-robind is that if you server goes down, DNS continues resolving for it. I would recommend use some balancer like LVS+keepalived.
Consider that multi layer solution:
| LVS + keepalived | | LVS + keepalived |
| |-------------- -------------- | Director 1 | | Director 2 |
| |----------------- ----------------- | IMAP/POP/LMTP | | IMAP/POP/LMTP | | Backend | | Backend |
\ /
\ /
\ ------------ /
-------| NetAPP |---------
------------Remember, directors and backends could run on the same machine. I have a lab running that way. Maybe I can help you deploy. On 07/23/2014 07:23 PM, Richard Hector wrote:
Hi all,
For some reason, I didn't go to http://wiki2.dovecot.org/NFS until now, and I'm starting to get worried ...
The plan was to have multple servers (MXes) receiving mail, and delivering via LMTP to multiple backend dovecot servers (with amavis in front of dovecot; LMTP both sides). Then we'd have multiple servers for clients to use IMAP or POP3.
This is more or less how the system already works, except with Courier IMAP, and postfix on the backends, delivering to maildirs with procmail.
But with the recommendation to use the Director for both IMAP/POP3 and LMTP - that starts to sound like I need a whole bunch more servers to run Directors and proxies, and even then it might not be a good idea to have different servers running lmtp and imap/pop.
One possible mitigating point is that our 'load balancing' is DNS round-robin, so a given client will probably stick with a single imap/pop server anyway, but if the user has multiple clients (desktop/mobile etc) then they may still hit different servers.
Can someone clarify best practice for a setup needing multiple servers for load balancing and redundancy?
Is Courier already likely to have been suffering these problems?
Oh, the NFS server is a NetApp Filer, if that matters.
I'm using dovecot 2.2.9 from debian wheezy backports, in order to get the quota policy daemon support.
Thanks, Richard