It's important to be able to monitor your production system's
health. You want to monitor the memory and file system utilization,
the system load, how much memory the processes use. Whether you aren't
running out of swap space and more. All these tasks are feasible when
one has an interactive (telnet/ssh/other) access to the box the web
server is running on, but it's quite a mess since different Unix tools
report about different parts of the system. Which means that you
cannot watch the whole system at the same time and it requires lots of
typing since one has to switch from one utility to another, unless
many connections are open and then each terminal is dedicated to
report about something specific.
But if you are running mod_perl enabled Apache server, you are in a
good company, since it allows you to run a special module called
Apache::VMonitor which provides most of the desired reports at
once.
