On Wed, 18 Oct 2000, John Sloan wrote:
> > There's almost no valid reasons
> > remaining in this modern world to ever use secondary MXers anyway, and
> > indeed many good reasons other than just this to avoid them altogether.
>
> I have sympathy with this viewpoint, but I don't think it is as true as
> you might think. There are yet still excellent reasons for having backup
> MXes.
For a busy host, it pays to have a backup MX standing right next to it,
for the following reasons:
(1) If you only have a narrow pipe from the outside world, it is better to
keep the mail trickling along it all the time, to avoid a huge flood
later.
(2) Incoming mail accumulates on the backup, which is close, instead of
waiting on dozens of servers round the world, some of which may be at
the end of slow or intermittently connected lines. When the primary
recovers, it can get the accumulated mail quickly.
(3) Without a backup, when the primary recovers it is liable to be hit
by a very large number of simultaneous incoming SMTP calls from all over
the world, which may impact server and/or network performance. Years ago
(before Exim), I saw a server crash when this happened, because it
didn't have adequate limiting mechanisms. In contrast, the transfer of
mail from one backup host can be done in a controlled manner.
--
Philip Hazel University of Cambridge Computing Service,
ph10@??? Cambridge, England. Phone: +44 1223 334714.
