System load very high

Jeff A. Earickson jaearick at COLBY.EDU
Tue May 20 14:10:15 IST 2003


   Some things I've learned, from the list, suggestions from Julian,
and hard knocks.

a) Run a name-server on your mail system, at least in caching mode.  Give
it lots of memory.

b) Set the Incoming Work Dir in MS to ramdisk if you can (eg, /tmp on a
Sun box).

c) turn off auto-whitelisting in SA, and maybe bayes (I like bayes).

d) Watch your RBL's carefully, both for your mail software and in MS.
DNS timeouts to an RBL can kill you.  Local name service can help this.
Get rid of RBL sites that don't respond quickly.

e) reduce the number of children in MS.  I have a two CPU Sun E220R
(450 MHz cpus).  I only run with 4 children, not the ten suggested in
Julian's conf file.

f) reduct the number of messages per MS scan.  I only run 25, instead of
the default 100.  The idea here is that MS takes smaller nibbles at the
(backed up), but moves each nibble over to mqueue faster.  The
settings of fewer children and smaller messages per scan reduces my system
load and overall thrashing, BUT the backlog in stays bigger longer.

g) Try sophossavi instead of sophos.  Or another anti-virus engine.

h) Maybe tweak with your sendmail settings.  I recently turned on the following
sendmail settings:


The idea here is to cut down on the I/O that sendmail does and hold more info
in memory.  The Bat book talks about the first two for performance (and cautions
against using the third option).  Julian says that sendmail drags without
SuperSafe=True.  I haven't noticed much difference myself.

i) Buy a bigger, faster box.  I'm looking at moving my email to a Sun V1280
with 4 CPUs, roughly 4 to 6 times faster than what I've got now.  I have
to do this every two years because email has become such a computer intensive

In summary:  frankly I find MailScanner to be more CPU intensive than I/O
or network bound.  More/faster CPUs seems to be the order of the day.

--- Jeff Earickson

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