On Tue, Feb 22, 2011 at 07:29:23PM -0800, Robert Goodyear wrote:
> As I understand it, the RELAYHOST parameter will allow an FQDN that,
> when bracketed, can skip MX lookup and just return the DNS result. If
> I use roundrobin A records for my mesh of MTAs out in my datacenters,
> I've got a reasonable randomization going on. If I use MX records of
> equal weight, Postfix will do the randomization (assuming I've not
> disabled that in general with the SMTP randomize param elsewhere.)
Randomization happens among all equal weight addresses. Multi-homed
hosts are implicity equal weight MX hosts, so they are also randomized.
> So, the downside of direct addressing of the roundrobin A record of
> my MTAs might be a lack of fallback that would have been described in
> my MX record. But for HA outbound stuff, I've got bigger problems if
> one of my MTAs on the edge goes down, so let's ignore that for now.
If you have enough equal-weight IPs, there is no need for lower-weight
IPs. Just run all the servers "hot-hot".
> With that assumption, it seems like MX versus roundrobin A addressing
> of my MTAs is pretty much equally performant
Not "pretty much", "exactly as".
> save for the failover inherent in MX.
No additional "failover" unless you want some hosts to receive mail
only when it fails to deliver to others. I prefer hot-hot.
--
Viktor.
