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 are running out of swap space, and so on. 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. All of this means that you cannot watch the whole system at the one time; 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, then you are in good company, since it allows you to run a special module called Apache::VMonitor thatprovides most of the desired reports at once.