http_load does not replicate heavy load; it replicates a DOS attack. It generates N requests every second without waiting for the previous N requests to comple

http_load does not replicate heavy load; it replicates a DOS attack. It generates N requests every second without waiting for the previous N requests to complete. Actually, it never waits for requests to complete. It kills them so the http server has no where to send data. With Tomcat, this causes hella errors in the logs. It's just not an accurate stress test. ab is okay but I found it was more difficult to ramp it up to really stress the server. I prefer siege (http://www.joedog.org/JoeDog/Siege http://www.joedog.org/JoeDog/Siege) because it performed well, produced useful output (ab's output is pretty good too), and was convenient. We used these three to test a new app stack for yellowpages.ca a couple years ago. siege became the standard in the end. We also tried JMeter which performed pretty well but the GUI/XML configuration was inconvenient (it's a complicated development environment).