Load average high!!!

[James Gray]

Ugo Bellavance wrote:
>>-----Message d'origine-----
>>De : Vinayakam Murugan [mailto:vinayakm at THEARGONCOMPANY.COM]
>>Envoyé : 15 mars, 2004 12:15
>>À : MAILSCANNER at JISCMAIL.AC.UK
>>Objet : Load average high!!!
>>
>>
>>Hi
>>
>>One of our customers has a PIII server with 128 MB RAM and a 
>>20 GB HDD. They
>>were using MailScanner 4.21 and clamav 0.60 till today. They 
>>used to face the
>>problem of load averages shooting up quite frequently. I 
>>upgraded them to
>>MailScanner 4.28.6-1 and clamav 0.67 today. Some time after 
>>the upgrade, I
>>noticed that the load average was still shooting up to above 
>>5. I stopped
>>MailScanner. The load average came down almost immediately. I 
>>was able to
>>convince the guy to upgrade to 256 MB RAM. Things seem stable now.
>>
>>Is this hardware configuration low for a server that is a 
>>internet router and
>>a mail server  for < 1000 messages a day?
> 
> 
> A load of 5 is not that bad.  The best performance measure you can use is message delay, I think.
> 
> A load of 5 only means that at all times, 5 processes are waiting for some resource.  However, if those 5 processes are MS processes...
> 
> I think ram can really be a bottleneck.
> 
> Once it starts swapping, it can really kill your server.
> 
> How many max child process?  I don't think you'd need more than 1...

I can concur with Ugo's suggestions with some real-world experience 
running MailScanner on low spec servers.  I have a Celeron433 with 512MB 
  RAM running MailScanner+SpamAssassin+McAfee and it's also the MySQL 
server as well.  It started life with  128Mb RAM which was totally 
inadequate.

The mail server handles <1000 messages with only one MailScanner child 
and hasn't had any problems.  Even during the last Netsky outbreak, 
system load was rarely above 0.5.  If RAM is scarce (<256MB) and volumes 
are low then run a single child with a 5 second check interval - this 
seems to be most economical trade-off between speed and RAM conservation 
(at least with my equipment).

My 1300+ custom SpamAssassin rules means that each MailScanner child 
occupys about 40Mb RAM.  Running more than 2 children on my Celeron box 
means that BOTH MySQL and MailScanner start paging like mad, and 
subsequently crucify overall performance for both of them.

YMMV.

Cheers,

James