[Discuss] cluster DNS servers

[dsr at randomstring.org (Dan Ritter)]

On Fri, Mar 22, 2013 at 09:50:16AM -0700, Dave Peters wrote:
> It's for mail server and could not use cache dns. 

I suspect there's a translation error here.

Normally a mail server would want a caching resolver either on
the same host or nearby, because mail servers do so many
lookups.

You could have a non-caching resolver, but that would be silly.
(Limited exceptions apply.)

And there's no particular relationship between auth dns and a
mail server.

So I'm going to assume -- and please, tell me if I'm wrong --
that you have a bunch of mail servers that all need reliable,
quick resolver service.

The most resilient method would be to equip each of the mail
server hosts with its own local resolver. This is inefficient in
the sense that the cache won't be shared between machines, but
for any reasonable number -- up to a hundred, let's say -- the
increased traffic really won't make much difference. It's very
small compared to the bandwidth being used for mail.

This is a very simple config for BIND, tinydns, or indeed any
other caching DNS server. I recommend it to you. Very little
can go wrong after you've set it up and tested it.

The next best method would be to use a group of DNS servers that
had failover for the service IP address. There's no need for
loadbalancing unless you are a much, much larger operation than
I suspect, so something very simple like heartbeat will do for
the failover portion.

-dsr-