[ On Monday, June 30, 2003 at 21:35:27 (+0100), Giuliano Gavazzi wrote: ]
> Subject: Re: [Exim] mirror MX
>
> All well, but you are forgetting the network. The primary would need
> two independent network connections.
No, it doesn't. E-mail reception is the very least of your problems.
E-mail storage and IMAP store reliability and availability are your real
concerns and those are also where you are most vulnerable.
If you want highly reliable and "available" e-mail reception (and
assuming you already have a highly reliable and highly available
back-end to store it and manage it), then you have one heck of a lot
more to worry about than just getting two independent network
connections. Such configurations have extremely high setup costs and
extremely high maintenance costs if you want to try to do it "right"
(and there's absolutely no advantage to doing such a thing on the cheap
-- e-mail reception is the very least of your problems)
> So I am still open to suggestions that do not imply investing
> thousands, when two ordinary (not cheap PCs) machines can do an
> excellent job.
If you're doing this on the cheap then your best option is to just build
yourself a nice reliable server with mirrored disks (RAID 1+0 if you
need multiple disks for capacity and/or efficiency), invest in a good
adequate capacity DLT or SDLT tape drive and make sure you have good
off-site storage for your backup media. Buy an on-site service contract
and/or your own spare parts.
On the network side make sure you have a good solid SLA for your
connectivity and make sure you buy service contracts and/or spares for
all your own networking equpment too. I.e. let the ISP worry about
redundancy and about paying for downtime.
Finally make and test good solid disaster recovery plans, including
off-site restoration if that's part of your requirements.
Everything else that you're thinking about is a waste of time, energy,
and money. Unless your business will literally lose thousands of
dollars per minute there's no sense in going any further. Do a proper
risk assessment before you go wild with unnecessary ideas.
(FYI the next logical step, if you have the requirements and the cost
justification, is a hot-standby server which is, as I've already
detailed, kept in sync with the primary using a constantly restarting
rsync script)
--
Greg A. Woods
+1 416 218-0098; <g.a.woods@???>; <woods@???>
Planix, Inc. <woods@???>; VE3TCP; Secrets of the Weird <woods@???>
