[CentOS] Load balancing email?

Nathaniel Hall lists at nathanhall.net
Tue Oct 25 23:31:08 UTC 2005


Craig White wrote:

>On Tue, 2005-10-25 at 17:17 -0500, Nathaniel Hall wrote:
>  
>
>>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.
>>    
>>
>----
>Let me see if I get this straight - OP asks about multiple MTA & dns/MX
>records and your answer is about MUA's and delivery agents. Good thing
>at least we all speak English. 
>
>OP - your logic is good - should work. I hesitated to answer since I
>have no first hand experience with multiple MX records of same value for
>priority.
>
>Craig
>
>
>  
>
His e-mail, as stated in the Subject and implied in the message was
about load balancing.  I gave a summary of my current setup that is
almost completely load balanced and redundant.  As a security
administrator, I partially based my recommendation on the fact that you
can (fairly easily) upgrade systems without taking the mail system
down.  I also see that as being part of load balancing (if one isn't
there, the other takes over the load).

--
Nathaniel Hall, GSEC
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