Pavel wrote:

> Hello,

> I'm using amavisd-new 2.4.3 with SA 3.1.7, Postfix 2.2.10 and clamav 
> 0.88.7 - so everything should be pretty up-to-date. I'm facing 
> performance problems, so I'd like to ask several questions. Sorry for a 
> mess, I have no more stamina to sort them any better :-(

> I have quite standard configuration, with the exception of DCC plugin 
> turned on and Razor/Pyzor off (we are running local DCC servers so the 
> response should be really fast).

> tail -f /var/log/maillog |perl -ne 'chomp; /amavis.*, (\d+ ms)$/ && 
> print "$1\n"'

> Are such times normal for 2.6GHz Opteron? What should I do to decrease 
> them? SA is configured for Bayes and AWL DB in MySQL, I have local DNS 
> cache, dedicated filesystem for mail spools.

> My load avg is about 2 with network tests turned on and mail queues 
> slowly filling.

If I'm not mistaken, a load average of 2 for dual core system is the
same as a load average of 1 for a single core system, so I think
things look good here.

> When I try to turn network tests off, load goes to cca 
> 18 and queues start to empty again, but the ratio of catched spam goes 
> down as well.

So the network tests are adding a necessary delay that keeps SA from
saturating your CPUs.

> Should I run more amavis servers with network tests on? I 
> already have 32...

Maybe. Considering the SA delays, CPU load average and hugh RAM I
might try it.

> I don't see any signs of IO/CPU/RAM problem (8 dual-core Opterons and 
> 32GB RAM should be enough!), 100Mbps link is saturated at about 4%. From 
> tcpdump on port 53 I can see delays in DNS responses, but they are not 
> tragic.

> I've tried to move tmp dirs of amavis and clamav to ram with no visible 
> effect.

So one might deduce your disks are not a bottleneck. If you increase
the number of processes and continue to use ram, you have to be
careful it's large enough. Sometimes using ram is not worth the risk.

> I don't know why SA thinks network tests are disabled - they shouldn't,
> or at least I don't have them turned off in both 
> /etc/mail/spamassassin/local.cf and /etc/amavisd.conf. I'm not using 
> user preferences for 'amavis' user - as far as I know.

As of SA 3.1.6 --lint turns off network tests. You now have to feed a
real message to spamassassin.

See this post:
http://marc.theaimsgroup.com/?l=amavis-user&m=116108763611148
but remember that you are using spamassassin and not a daemonized
scanner, so you can ignore stuff like how long it takes to load rules.
The whole thing may have inaccuracies but should prove to useful
regardless.

Since you mentioned MySQL. I will assume you have done some tuning,
but if not: If using MySQL >= 4.1, use MySQL and not SQL here:

bayes_store_module       Mail::SpamAssassin::BayesStore::MySQL

and these may be of interest (especially if you are using innodb):
http://www200.pair.com/mecham/spam/mysqlspeed.txt
http://www.mysqlperformanceblog.com/2006/09/29/what-to-tune-in-mysql-server-after-installation/
http://www.mysql.com/news-and-events/newsletter/2003-11/a0000000269.html

MySQL crawls if using innodb and the default innodb_buffer_pool_size
of 8M. Just increasing it to 128MB makes a hugh difference.

I assume you prune your AWL data on occasion?

> If anybody sees anything bad or has some tip for me, I'll be really
> grateful.

> Thanks!

Dictionary attacks and joe jobs appear to be increasing exponentially.
Do you use anything to help prevent the really bad stuff from getting
in the front door in the first place, like selective greylisting or a
policy daemon like policyd-weight? I understand this is not always
possible when a large variety of customers are involved but they can
make a big difference.

Gary V


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