Date: Fri, 25 Apr 1997 14:24:33 +0100 From: Alan Judge <Alan.Judge@indigo.ie> To: freebsd-isp@freebsd.org Subject: Large POP/SMTP server configurations Message-ID: <199704251324.OAA11999@indigo.ie>
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[Since we're hoping to transition as many of our service machines as possible to FreeBSD, this seems like the place to ask.] We're currently considering options for expanding our core mail service. The size of our userbase means that it's becoming less and less possible to support all our POP and user-related SMTP activity on a single machine (we've already offloaded most of the incoming and outgoing mail handling). (Our current service is a twin-cpu SS-20 running SunOS and is creaking at the seams, and will start hitting UID depletion problems before long.) I'm looking at options for upgrading and focussing on chucking the Sun gear and using PCs and FreeBSD (as we've already done for other services). I'd like to take this opportunity to spread the load across multiple machines, as I'm not sure how many users even a high-end PPro box will support. We don't want to make things complex for customers (or our helpdesk staff), so we want the solution to appear as simple and transparent as possible. A number of options come to mind: - Share the mail spools using NFS, either using a dedicated server like a NetApp or Auspex or using a dedicated FreeBSD box on a private 100MB network. Use multiple front-end machines to access. This has the advantage of being simple to manage, fairly reliable, and easily expandible. The lack of NFS locking, unless that's been fixed, may make this hard to do with FreeBSD, though I suppose you could reconfigure the applications to use file based locking. I don't like the idea of NFS in a production environment, but in a controlled setup like this, it should be OK. - Shared the POP boxes and load between machines. Use aliases on the incoming mail machines to make sure that a given customer's mail arrives on the right machine. The problem here is making POP work if all customers using the same name to connect. Our thoughts here are to use some sort of light-weight POP redirector that hashes or looks up the incoming username and picks the correct back-end machine to connect to. I haven't seen any software to do anything like this (anyone??), and I'm unsure about the performance aspects. - SMP with more than one PPro in the same box. I'm not sure that the SMP stuff will be ready for production use in time for us. Ideas/comments? What are other ISPs out there doing, and how might this be done with FreeBSD? Having moved so many services to FreeBSD, I don't really want to have to backtrack and get a big Sun or SGI box to do our core POP/mail stuff. -- Alan Judge Phone: +353-1-6046901 Indigo Internet Services Fax: +353-1-6046948
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