As a web administrator, we need to manage our server for a better performance. Of course we need an application to monitor our server.
I found a great software for server monitoring at Hyperic. They have the Enterprise Edition for large web infrastructure and the Open source one.
HQ Enterprise can manage every major operating system, and over 75 of the products and technologies most commonly found in web infrastructures. And of course, you could try the trial edition :).
The second one is the open source edition. It provides all fundamental capabilities for managing web applications. Powerful, reliable, and free, open source HQ is supported by a vibrant community of web operations professionals.
Just try it. You will never know till you have try this system management application.