Date: Sun, 26 Sep 2004 15:28:31 -0400 From: Chuck Swiger <cswiger@mac.com> To: Eric Crist <ecrist@secure-computing.net> Cc: freebsd-questions@freebsd.org Subject: Re: Backup Mail Server Questions Message-ID: <4157185F.1000805@mac.com> In-Reply-To: <493F1EDF-0FE0-11D9-A586-000D9333E43C@secure-computing.net> References: <493F1EDF-0FE0-11D9-A586-000D9333E43C@secure-computing.net>
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Eric Crist wrote: [ ... ] > One of my friends needs backup DNS/Mail in the even their connection > goes down. How do I go about setting it up so that his user base (about > 80 users) will not see any problems in mail transmission and reception > if their primary servers go offline. I would like mine to automatically > pickup the slack. Setting up redundant DNS is trivial: DNS is designed to do that. Setting up a backup MX is easy. It helps a lot if both mailservers are configured the same, and it is important that they have near-identical anti-spam and virus-filtering technologies. Setting up a truly redundant POP/IMAP reader box is extremely hard. To solve this problem for a local network, one normally uses a shared NAS box: in your case, this effectively requires one to set up a network-distributed filesystem, or some near-equivalent: for instance, a parallel database for mail stroage would serve as well. All sorts of nasty issues-- like the security of the data going between the two fileservers, or DBs, or whatever; significant added latency due to the storage mechanism confirming updates have propogated; etc appear. My opinion is that it's better to go with a primary mail reader box and make very certain that box doesn't go down by using redundant hardware and a backup network link is easier and less likely to suffer from the "lets create a complex system with lots of moving parts which never gets fully tested and thus breaks in some weird way when the unexpected happens" syndrome. :-) -- -Chuck
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