[Dovecot] Multi Server Exim/Dovecot and NFS

[Roland Rosenfeld]

> The only issue I see right now is Dovecot index file write bashing
> if a user accesses their mailbox from multiple locations at the same
> time, and I gave that example in the previous post.  That seems to
> be more and more common these days but still not the norm for 80%+
> of the mailboxes we have.

We have a similar setup and solved the problem for us this way: 

- The delivering mail servers (postfix+dovecot) don't write any index
  files, so we can use round robin here.
- We have an additional layer of proxy servers between the
  loadbalancers and the dovecot IMAP servers, that try to make
  sessions sticky.
  For this we use the IMAP/POP3 proxy code of nginx with a PHP script
  that does some database voodoo, normalizes the user name and based
  on all this decides which IMAP backend server to use.
  This is based on the username (not the IP), so it is sticky for
  multiple IMAP and POP3 connections from different IPs.
  I think dovecot director should be able to do similar things (our
  setup is a little bit older and needs some more flexibility).
 
Tschoeeee

        Roland

-- 
Roland Rosenfeld  -  Content Delivery  -  NED  -  Technik
NetCologne Gesellschaft für Telekommunikation mbH  -  HRB 25580, AG Köln
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