Re: [exim] Greylisting - using Exim new features - ratelimit…

--On 11 July 2007 06:57:20 -0700 Marc Perkel <marc@???> wrote:

>
> I'm using a different failover system. I have a main server on the low
> mx and several backup servers on the next highest mx.
>
> dummy0.junkemailfilter.com - 10 - semi-dead IP
> mx.junkemailfilter.com - 20 - main server
> mx.junkemailfilter.net - 30 - multiple backup servers
> mx.junkemailfilter.org - 40 - several IP where I log connect attempts
> dummy1.junkemailfilter.com - 50 - several IP where I log connect attempts
>

Hmm, that's just a case of having backup servers. Works fine for ordinary
SMTP, but isn't good enough for MUAs. When we set up our cluster, we set up
the 4 machines on a round-robin DNS, so smtp.sussex.ac.uk points to four IP
addresses. That seems to work well with MTAs, but doesn't work at all with
MUAs.

In order to provide high availability message submission, all four IP
addresses have to be available at the same time. That's why we introduced
IP failover. In theory, any one of the four machines could support all four
SMTP IP addresses at the same time.

We use spread/wackamole for failover, and it works really quite nicely,
though not perfectly. I'd estimate that downtime is reduced by an order of
magnitude.

--
Ian Eiloart
IT Services, University of Sussex
x3148