[BlueOnyx:05266] Re: Secondary mail server

[rodrigo at xnet.mx]

Also you migh configure database on your secondary websites

Youll get load balance but not redundancy


servicio email movil Blackberry
by xnet.mx

-----Original Message-----
From: "David Thacker" <David at thackernet.com>
Sender: blueonyx-bounces at blueonyx.it
Date: Fri, 20 Aug 2010 10:10:02 
To: BlueOnyx General Mailing List<blueonyx at blueonyx.it>
Reply-To: BlueOnyx General Mailing List <blueonyx at blueonyx.it>
Subject: [BlueOnyx:05265] Re: Secondary mail server

> Many thanks for all the info.  I'd appreaciate it though if you could
> explain what exactly would happen in the scenario I described, and why
> mail will "randomly" end up on each server.

You guessed what will happen in your own original question:

>> I'm hoping), or will it be delivered to the redundant mailboxes on the
>> secondary server?

Mail will get delivered to the mailboxes on whichever server it first 
lands on, not queued for the primary server only.  Not pretty.


IF your client websites are completely static, and do not utilize any 
read/write databases or forums or anything like that, then you can achieve 
your goal (load balancing and/or quick failover of web, queued email 
waiting for main server to come back up) with the right config, no extra 
software needed. If you have any dynamic data driven websites, you'll need 
to go with the clustering solution Chris presented.

Quick & Dirty Failover Web for Static Sites

- Configure main and backup servers as primary DNS servers, not 
master/slave. You need to configure all the records on each server 
individually.
- Set A records of hosts to correct vsite IPs corresponding to that 
specific server (backup server vsite IP not the same as main server vsite 
IP). That yields web load balancing and failover.
- Set the MX records to deliver to main server at highest priority, backup 
server at lower priority, and make the "mail" hostname A record point to 
main server only.
- Duplicate the vsites on both servers BUT make sure that the USERS only 
exist on the main server. The backup server should not have any users.
- MUST ensure that the site domains are listed on the backup server in the 
"Relay Email From Hosts/Domains/IP Addresses" email server setting.

When mail gets received on backup server, it will be queued for delivery 
to user on main server. If the main server is alive, that will happen 
immediately. If the main server is offline, mail will just get queued on 
the backup server until the main server comes back. Default queue duration 
is 5 days I think, you can change that in sendmail config. When a user 
browses a website, they will hit either the main or backup server, 
depending on which DNS server their system queried -- should be completely 
seamless to the user if you have the same web data on both servers. If the 
main server (including DNS) conks out, website users will just be hitting 
the backup server, until the main server is revived.

Your customers will of course be unable to receive their email while the 
main server is down, so they will know there is a problem, but website 
visitors will still be served, and customer emails should be queued until 
the main site returns.

David Thacker 

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