The following are some of the commonly used benchmarking tools:
A useful tool, capable of doing everything from simple
requests for a single file to simulating client sessions.
Available from:
http://www.hpl.hp.com/personal/David_Mosberger/httperf.html
A simple benchmarking tool, distributed with the Apache Web
Server. The source is in the file src/support/ab.c
in the Apache source tree.
A Perl script for automating a series of httperf tests against
the same server (or a pair of servers). It parses the output
of httperf, and summarises the results of the tests in a CSV
or TSV file that can be imported directly into a spreadsheet
for further analysis/graphing. Available from:
http://www.xenoclast.org/autobench/