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Date:      Wed, 22 May 2002 16:41:23 -0700 (PDT)
From:      Matthew Dillon <>
To:        Omar Thameen <>
Cc:        FreeBSD Hackers List <freebsd-hackers@FreeBSD.ORG>
Subject:   Re: tuning a CPU bound server
Message-ID:  <>
References:  <> <> <>

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    I think this has gotten off-topic.  I am going to go back and respond
    to the original posting.

    When I was doing BEST Internet we had very similar problems with our
    mail servers.  We were constantly cpu-bound.  I was constantly fiddling
    with it (sendmail in this case).  For months.  For years, in fact.
    We did things like put sendmail's dns cache in a ramdisk, split the
    queues, tuned the retry periods, etc.

    The fiddling ultimately produced incremental gains but in retrospect it
    was a waste of time.  The solution that worked... *REALLY* worked,
    was two throw more horsepower at the problem.  Even more so the solution
    was to simply add more servers.  I created a set of 3 incoming mail
    servers and a set of 3 outgoing mail servers.  The mail servers were
    load balanced simply with an IN A (DNS) round robin, which worked
    wonderfully.  Separating the incoming from the outgoing servers allowed
    me to do relatively simple tuning of the incoming servers for incoming
    traffic, and relatively simple tuning of the outgoing servers for
    outgoing traffic.  One also gets the added perk of being able to
    turn down individual servers for maintainance without taking down the
    entire company's mail system in the process.

    So what I would recommend is that you add another duel-cpu server and
    load balance the traffic with DNS.  It's worth doing some tuning but I
    would not waste my time at it.


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