Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

we have a very high load System with round about 8.5 Million User per day. Actually we have 8 Apache2 Loadbalancer (Ubuntu 10.04.3 LTS x64 via DNS-RoundRobin) which are sending the traffic via AJP1.3 to 20 Workers. On this workers our self-written Grails-Webapplication is running on a tomcat7 + java7 server (Ubuntu 11.10 x64). The Application is Logging to a local postgresql 9.1 database. All Servers are hostet on Hetzner Germany an have an Intel® Core™ i7-2600 with 16GB's RAM an 2x3TB Raid 1 HDD.

At Prime-Time (6(pm) till 12(pm)) we have sometimes serious performance bottlenecks but the hardware is not the Problem. CPU is max at 50%, load max. 2.5 and RAM only used 3-4GB max. But i have no Idea, where is the Problem.

Here is an excerpt of my server.xml:

<!-- Define an AJP 1.3 Connector on port 8009 -->
<Connector  port="8009"

At peak the Tomcats handle 400-450 Accesses per second. Have anyone some tips how to optimize the performance of Apache + mod_jk + tomcat7?

share|improve this question
i would check tomcat's startup config as well. catalina opts and stuff – Alfabravo Dec 14 '11 at 10:28
We have set the ulimit till 65536 in Tomcat's Startup, because in the past we had problems with it. Java_Opts we have also edit: JAVA_OPTS="${JAVA_OPTS} -XX:+UseConcMarkSweepGC" JAVA_OPTS="$JAVA_OPTS -Xms512m -Xmx2048m -XX:MaxPermSize=256m". Catalina_opts are default at this Time. – FTV Admin Dec 14 '11 at 13:29
1.) I would reduce access to tomcats putting static resources to be served by apacheHTTP itself; 2.)Would check GC with -XX:+PrintGCTimeStamps -XX:+PrintGCDetails; 3.) Depending on this, improve generation management with JVM (…) – Alfabravo Dec 14 '11 at 13:52
ConcMarkSweepGC can cause long delays if it fails to finish the concurrent GC in time and has to do a full stop-the-world collection instead. You really need to log your garbage collection and analyse the logs carefully. – Mike Scott Dec 14 '11 at 14:47

Garbage collection would be my guess -- it can cause bottlenecks on loaded Java servers. Have you studied your garbage collection logs to get an idea of the delays involved? What are your garbage collection settings

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.