I am actually going through the first stages of implementing your Scenario1. There is small difference: there will also be 2*Postfix relays also on the Dovecot Proxies. This allows placing them in a DMZ such that the "real" Dovecot/Postfix servers are placed away from the WAN.
After much arguing and thinking I decided to go with this option as the most basic and possibly the simplest way to achieve MY goals: the same setup to ease configuration (mostly done by users these days)
- fault tolerance of the entire system such that a failure will not impact mail delivery/access.
- distribute users on at least two Dovecot servers to help when peak times arrive.
- Ability to expand easily if demand rises
- No use of custom hardware
- Both internal (LAN) users and "away from office" (WAN) users will "see"
I should say that other more complicated setups like full blown clusters and distributed file systems have been rejected due to their complexity (and the fact we do not have experience with them). Our user base is around 3-4K of heavy users.
Andreas
On 29-05-2013 00:23, Romer Ventura wrote:
Hello,
I've been thinking about the best way to achieve load balancing and making my mail servers highly available. So far I believe I have 2 scenarios:
Scenario1: This should allow any to lose any of the servers and clients still have access to their emails (although I am not sure how the indexes would react to this and sudden disconnection)
2 Dovecot Proxy servers, using a virtual IP to where theclients will connect to from the WAN and LAN
2 Dovecot+Postfix servers with local cache2 NFS servers and synced with dsync (mirror, 1 serverwrites to its own NFS and changes synced to the other via dsync)
Scenario2: Pretty much as above on the back end. However, with this there is no way to load balance users.
2 Dovecot+Postfix server with local cache2 NFS servers synced with dsyncMake use of DNS MX record priority to provide access tosecondary email server
Anyone care to comment?
Thanks.