Re: Can we build a proper email cluster? (was: Re: Why is debian.org email so unreliable?)
On Fri, 15 Oct 2004, Russell Coker wrote:
> You seem to have entirely misunderstood what I wrote.
And I think I had misunderstood you, but your message cleared things up...
> Having four engines on a jet rather than two or three should not be expected
> to give any increase in reliability. Having two instead of one (and having
> two fuel tanks etc) does provide a significant benefit.
[...]
> With mail servers if you have a second server you have more work to maintain
> it, more general failures, and you have no chance of saving anyone's life to
> compensate.
>
> Finally consider that one of the main causes of server unreliability is
> mistakes made during system maintenance. Increase the amount of work
> involved in running the systems and you increase the chance of problems.
In other words, your point is not that two MX are not more "resilient to
failure", but rather that the work of administrating them is not worth the
gain in resilience ?
That would depend directly on what sort of downtime you want to tolerate on
the mail system. IMHO, >4h downtimes in Debian's mailsystem is something to
avoid at any reasonable cost, and that would require either two active MX,
or a ready-to-deploy MX kept inside the closet (which is more dangerous
maintenance-wise than two live MX IMO) for the worst-case scenario.
--
"One disk to rule them all, One disk to find them. One disk to bring
them all and in the darkness grind them. In the Land of Redmond
where the shadows lie." -- The Silicon Valley Tarot
Henrique Holschuh
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