round-robin and multi MX practicalities

David Zade dzade at rcn.com
Wed Feb 23 00:58:18 UTC 2000


Beware, I do not believe roundrobin will work for failing over to a backup
server.  It just hands out the addresses in rotating order.  It will still
handout the address of the dead server.

Second, mail clients, use\d on the user desktop, don't typically use SMTP to
receive messages, they use POP3, IMAP, or a custom protocol,  They may use
SMTP to send, but I think that address is resolved to a specific server 'A'
record.  The MX record is used by SMTP server to forward mail to other SMTP
servers.

You want a load balancing services, either one that redirects packets, or
provides s DNS service.  Either way the load balancer would have to monitor
server (and service) availablility, and alter forwarding decisions based on
the monitor info.

DAvid zADE
dzade at rcn.com
Alex Miller <bind at lists.cybergood.net> wrote in message
news:003001bf7d84$9d2d25c0$867c06d1 at aranea.cybergood.net...
> I had a server go down recently. It's the
> second failure I've had in 6 months both
> times were my error. What a different and
> refreshing world Linux is (as compared to
> Windows not other Unixes), when I can no
> longer blame the OS for down time!!
>
> Anyway, I want to set up a SECOND server
> for the next time I screw up.
>
> Round-robining should work fine for a web
> server, if one is down, the other is available,
> that I understand, but multiple MX records
> are a different story.
>
> If a user has not picked up mail on server A
> and then server A goes down, and mail gets
> handeled by server B, mail might get lost
> when server A goes back online. All the
> mail that collected on server B during server
> A's absence, will not be collected once server
> A is handling collections.
>
> Therefore I must, I presume, synchronize the
> user mail on server A and server B. This could
> be rather scary I would think, and I imagine
> all sorts of nasty file locking problems, etc.
>
> What solutions are being used to use two servers
> for web redundancy and email redundancy?
>
> Alex Miller
>
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