[CentOS] Load balancing email?

[Nathaniel Hall]

Benjamin Smith wrote:

>Currently, we have two mail relays for inbound messages, and a third for POP. 
>
>The inbound messages go thru all the CPU-intensive anti-spam stuff, and then 
>they relay it to the POP server for pickup. 
>
>Currently, one of these is the "primary", and the other is "secondary", and 
>I'd like them to be considered more or less as equals, since the "primary" 
>system is getting beaten pretty hard. 
>
>The DNS zone file says something like this: 
>
>###############################
>@isp.com 
><SNIP>
>                IN      MX      100 mx1.isp.com. 
>                IN      MX      1100 mx2.isp.com.
><SNIP 
>################################
>
>I seem to recall that I make them act as "equals" by simply changing this to 
>
>###############################
>@isp.com 
><SNIP>
>                IN      MX      100 mx1.isp.com. 
>                IN      MX      100 mx2.isp.com.
><SNIP 
>################################
>
>so that they both get about the same amount of inbound messages. Has anybody 
>here actually done this? How well does this work as far as failover if either 
>system fails? 
>
>-Ben 
>  
>
I actually recommend using a Cyrus system.  We are able to handle about
20,000 accounts with the following servers:

3 front ends (Horde, IMAP, Spam Assassin, SMTP, etc load-balanced at the
firewall)
2 storage servers (actually stores the e-mails)
1 MySQL server (Used for Horde)
1 list server (for MailMan)

This can easily be added to.  We use it a lot so that we can remove a
system from the load balance and upgrade one server at a time.  We can
eventually take all but one out and have them upgraded and then swap the
last one with all of the new servers.  It appears to be seamless to the
users and sure helps with being able to do maintenance at any time of
day and you don't have to have overly powerful servers to get it working
well.

--
Nathaniel Hall, GSEC