Mailscanner and server load

kfliong kfliong at WOFS.COM
Thu Aug 26 09:24:31 IST 2004

I have just implemented SURBL. Server load shot up and stays around 30
making websites unaccessable. I have now edited SURBL to only check on
SPAMCOP_URI_RBL. I have disabled the other 3. Now my load averages around
12. This is still quite high.

BTW, after some monitoring using "top", I notice that my system is quite
RAM intensive. But "top" can't tell for sure. What other tools can I use to
see whether the highload is due to lots of disk accesses (due to not having
enough RAM).

At 03:26 PM 26/8/2004, you wrote:
>On Thu, 2004-08-26 at 03:55, David J. Duffner - wrote:
> >         #3 - DON'T PANIC on load averages.  We're using MRTG and
> MailScanner
> > MRTG and they don't agree with load averages, so you're not seeing a
> > realtime accurate report!
> >     But overall you're seeing
> > an illusion, we finally got a grip on it as MailScanner MRTG samples
> > at a different rate and is giving us a REAL average to work with on
> > loads.
>Just to explain that a little.  MailScanner-MRTG samples every five
>minutes and uses the five minute average load - thats the second load
>average figure given by top and w.  This is handy as it means it takes
>the average over its reporting period so is less prone to being messed
>up by brief spikes.  A word of caution - older MSMRTG's didn't work like
>that (it used the one minute average - which tended to be misleading).
>Upping the RAM to 1G is a good idea, depending on your message
>throughput you may be able then to put the MailScanner work directory in
>tmpfs - that gives a significant performance boost so long as you have
>enough physical ram (if it causes it to start swapping thats a bad
>You need to get a feel for whether your system is CPU bound or IO bound,
>the above trick will really help with disk IO related issues, network IO
>issues can be helped by running a caching nameserver on the box itself
>(very easy, theres an rpm for caching-nameserver I think, then you just
>point resolv.conf and
>A load average of 3 isn't necessarily a problem anyway, so long as mail
>is flowing with acceptable latency and you can cope with spikes.  Given
>that your machine was able to battle through the backlog that built up
>during your upgrade (hence the 30 load av) I'd say its not too
>concerning (I'd still add ram, do the tmpfs thing and run a
>caching-nameserver though).
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