Munin the tool surveys all your computers

Munin the tool surveys all your computers and remembers what it saw. It
presents all the information in in graphs through a web interface. Its emphasis
is on plug and play capabilities. After completing a installation a high number
of monitoring plugins will be playing with no more effort. Using Munin you can
easily monitor the performance of your computers, networks, SANs, and quite
possibly applications as well. It makes it easy to determine "what's different
today" when a performance problem crops up. It makes it easy to see how you're
doing capacity wise on all limited resources.