--On 9 November 2007 13:27:48 +0100 Adrian Chapela
<achapela.rexistros@???> wrote:
> Ian Eiloart escribió:
>>
>>
>> --On 9 November 2007 12:50:43 +0100 Adrian Chapela
>> <achapela.rexistros@???> wrote:
>
>> Provision of IP failover is highly dependent on the platform that
>> you're using. It's not required for MX availability, because remote
>> servers will try all your advertised servers. It is required for MSA
>> availability, because MUAs will not.
> Yes you are right, but if you have clients locally on your company, they
> must connect to a smtp server and DNS round robin it isn't the best
> solution to get hight availability (IMHO).
That depends what you mean by "client". If you mean an MTA attempting to
relay, then round robin should do reasonably well at low cost. If you mean
mail user agents (MUAs) then round robin doesn't help at all, as I said.
Absolutely right - DNS round robin does nothing for MUAs (mail clients).
Mail clients won't attempt to connect to a second IP address, so DNS round
robin does nothing to achieve high availability at all. It merely serves to
provide load balancing. Actually, if that makes the servers more capable,
then you may get some small availability gains.
So, for high availability you need to ensure that every IP address in the
round robin is highly available. For that, you need IP failover. For MX
hosts, you don't need IP failover because remote servers should try all the
available IP addresses.
>>
>> We use MacOSX servers. OSX has a reasonably easy to configure IP
>> failover mechanism, as long as you only have two servers. When we went
>> beyond two servers, we deployed spread and wackamole which make
>> failover configurations for any number of servers trivial. For
>> example, we have 12 imap server IP addresses, to ensure good load
>> balancing with either 4, 3 or 2 available hosts. Wackamole simply
>> needs to know what the addresses are, and endeavours to share them out
>> equally among available servers.
> Yes.. it sounds perfect...
>>
>> <http://www.spread.org/>
>> <http://www.backhand.org/wackamole/>
>
> Best regards.
--
Ian Eiloart
IT Services, University of Sussex
x3148
