mail at iaindooley.com
Tue May 10 20:13:22 CEST 2005
Brad Knowles wrote:
> At 3:27 PM -0700 2005-05-09, Tyler Strickland wrote:
>> That's entirely possible - the system is an old sun running sendmail.
> Older versions of sendmail can certainly have some issues in this
> respect. More modern versions work much better, but still require
> some additional configuration changes in order to get them to work
> better with large mailing lists.
>> I'm currently building a new mail server to replace it that should be
>> able to handle the load much better by running postfix on a
>> hyperthreaded Pentium 4.
> See the stuff in the FAQ about "performance".
> For one, HyperThreading almost always hurts performance and does
> not help. This is a seriously dain-bramaged idea that Intel had that
> never panned out, although they did get enough people interested in
> the concept that once AMD came out with a real dual-core chip,
> performance really has improved significantly.
> For two, you don't need CPU. You need RAM and disk I/O capacity.
> Not disk space, but I/O capacity. When an MTA receives a mail
> message, it creates one or more temporary files to store that
> message. When the message has been delivered, the temporary files
> are deleted. Between those two points, there may be many more file
> creations, deletions, and renaming operations just for that one
> Each of these types of operations are known as Synchronous
> Meta-Data Operations, and they require that the entire directory be
> locked against all other changes during the process of that
> operation. You would think that this would not hurt performance very
> much, but think of a turnstile going into a football stadium -- no
> matter how fast it operates, the simple fact that it only allows
> through one person at a time will mean that the total throughput is
> greatly reduced.
> A fast intelligent hardware RAID array with a large quantity of
> battery-backed write-back RAM cache and high-speed internal
> interfaces to high-speed drives with intelligent disk queueing (i.e.,
> SCSI with Tagged Command Queueing, or good SATA drives that actually
> properly implement a similar feature) can really help. A fast
> filesystem which optimizes synchronous meta-data operations can also
> But all this is covered in the FAQ, and you should read about it
> when you search for "performance".
> I will tell you that if you're trying to build a high-performance
> mail/mailing list server, about the worst possible mistake you could
> make would be to try to build the machine without first reading the
> information on this subject in the FAQ, and reading the various
> pieces of documentation that are referenced.
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