On 11/17/2011 12:15 AM, Alex wrote: > Hi, > >>> I built a dual-Xeon quad-core box with 8GB using fedora15 and >>> postfix-v2.8.5 and during various times during the day connections to >>> port 25 timeout or are very slow. The majority of times this happens >>> is under peak loads, but even times when it's not at capacity it may >>> do this. >> >> Often slow smtpd connections are caused by not having enough smtpd >> processes running. >> >> On your hardware, postfix will support thousands of smtpd processes. >> Use netstat or lsof to see how many connections postfix is handling >> when you experience slowdowns. > > It's in the hundreds.
The question is: is the number of connections your system is handling at peak nearly equal to the number of connections configured? If yes, then you need to configure more connections. If many of the connections are spambots, postscreen will help. That's what it is designed for. > When using amavisd-new, shouldn't the number of processes match the > number of smtpd processes? When using amavisd-new as a content_filter, the number of postfix smtp->amavisd feeder processes should be equal to (or maybe one less than for monitoring) the number of amavisd processes. This is independent of the number of smtpd input processes. > I think what I'm concerned about is having postfix receive more > messages than amavisd can process? Yes, that's a concern when using any content_filter, but really a separate issue. If you limit the input by using too few smtpd processes, connecting clients will get timeouts. Your system should handle 20~30 amavisd-new processes. Check the amavisd-new and spamassassin documentation and user lists for performance tips (90%+ of amavisd-new processing time is spent in spamassassin). -- Noel Jones
