On the PHPClasses.org blog Manuel Lemos has posted part two of his look at techniques to help speed up your site - a few things that you maybe hadn't thought of before.
In the previous article I talked about one important factor that often seriously affects the user perception of the speed of a site, which is the presence of content from external sites that slows down the load of pages, such as advertising and widgets. In that article I presented a technique that I am using to make external content not affect the user perception of the site speed. In this article I am addressing another factor that may also affect the user perception of site speed, but this time is related to aspects of the server side environment.
In this article he looks at things like other server-side background processes, throttling their CPU usage, throttling PHP's CPU usage and the use of a monitoring class to help you and your applications (and sysadmins) stay on top of what's happening with the server.