Questions on a redundant mail system
Hey!
We're about to re-design our mail system and are looking at various
hardware and software options for failover, redundancy and load
balancing. The solution I'd like to present consist of two or more
frontend servers handling all incoming requests, then forwarding them
to a number of backend servers depending on load.
I have a few questions regarding the design which I'd like to have
views on as some of you people around here have lots more experience
on this.
1) Frontend: Which is better: two frontend servers, each handling both
POP and SMTP connections together with DNS round-robin or separate
machines for POP and SMTP? They would handle incoming SMTP and POP
requests for about 15000-20000 people plus a lot of mailing from
websites with forms and such. We're currently handling approx. 150 000
POP requests each day and somewhere around 220 000 SMTP transfers.
2) Backend: Should one let the backend servers handle both POP/SMTP on
the same machines, or have separate machines for each service?
Pros/cons?
3) Backend: For redundancy purpose I want all servers to share the
same storage area, so if one backend server server goes down the
others will still be able to handle delivery to/from all mailboxes.
How do we solve this best? Some kind of NFS mounts, a hardware RAID
array, AFS? I think this is the most important question.
I've followed the Huge Email Service thread and found it very
interesting. The Jetcafe papers helped some, but it was _too_
large-scale and I'd like up-to-date info on filesystems and hardware
as well.
Thanks,
/erik.
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