Date: 14 Mar 1998 17:39:39 +0100 From: Benedikt Stockebrand <benedikt@devnull.ruhr.de> To: "Andras Tudos - Computronic, C3" <andras.tudos@computronic.hu> Cc: freebsd-isp@FreeBSD.ORG Subject: Re: Scalable mail server Message-ID: <87lnud8bw4.fsf@devnull.ruhr.de> In-Reply-To: "Andras Tudos - Computronic, C3"'s message of "Thu, 12 Mar 1998 21:31:04 %2B0100" References: <3.0.2.32.19980312213104.01060870@computronic.hu>
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"Andras Tudos - Computronic, C3" <andras.tudos@computronic.hu> writes:
> we have to scale our qmail based mail server (with a custom made www
> frontend) to multiple machines to be able to serve ~100000 users and more.
> Currently we have a single server based heavily overloaded system with
> 30000+ users. We have many plans, but I would prefer to hear how others
> would start to construct such a system. We build all the machines ourselfs
> (including PII based PCs, RAID, network) and write the necessary code.
What's your resource bottleneck? Until you've found out about this
you're only fighting with a blindfold on.
> All ideas, especially real world experiences are warmly welcome...
> (Especially file-system,
>From experience with news and UUCP: Do you happen to have a single
/var(/spool)?/mail directory holding all users mail boxes? If so,
split that up first. And if you've got a flat /home/* hierarchy, do
the same there, too. Files are searched via linear search on
directories, and that becomes *excessively* expensive with large
directories. Especially with UUCP-forwarding news servers this can be
absolutely devastating.
> user database and redundancy issues are critical.
RAID arrays are always reasonable for reliability issues.
> Would you use SMP with dual PIIs or 2.2.5?
Some SMP developers are probably going to kill me for this, but I'd
stay away from SMP if I can help it. The kernel SMP support may be
fine. Maybe the libraries are fine, too. But don't rely on every
single userspace program you use to work reliably on SMP systems. And
debugging problems that only occur twice a week isn't much fun,
especially on production systems.
Besides, I wouldn't really expect CPU load to be the limiting resource
anyway.
> NFS issues?
As a personal opinion: Don't. It's a resource hog. And if a machine
goes down this will cause heaps of problems on the remaining
machines.
> Postgres instead of passwd?
Do some performance analysis before you get into this sort of stuff.
Unless I'm mistaken the /etc/s?pwd.db should be reasonably fast except
when running pwd_mkdb to modify it.
Ben
--
Ben(edikt)? Stockebrand --- Un*x system administrator looking for a job
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