*BSD News Article 95264


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From: Alan Judge <Alan.Judge@indigo.ie>
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: FreeBSD for large POP/SMTP setups
Date: 14 May 1997 10:08:37 +0100
Organization: Indigo Network Operations Centre
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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 Network Operations Centre                Fax:   +353-1-6046948