Want to learn how to improve the performance of your Ubuntu Linux operating system? ExtremeTech published a guide on this subject, here's a snip:
The default Ubuntu Dapper Drake installation includes some basic processes that check devices, tune the operating system, and perform housekeeping. Some of these processes are always running, while others start up periodically. Occasionally you might see your hard drive start up or grind away for a few minutes—what's going on? On mission critical servers, serious gaming boxes, and other real-time systems, unexpected processes can cause huge problems; administrators should know exactly what is running and when. The last thing a time-sensitive application needs is for a resource-intensive maintenance system to start at an unexpected time and cause the system to slow down.