You come into work one day and as you sit down, your phone rings. It's one of the business groups complaining that the database is running slow. You check the server and find CPU at 80%, 800 pages/sec, disk IOps of 230 and 124 transactions/sec. Is the database the problem? 

Good DBAs know that baselines are essential. If you don't know what values to expect from your server, it's often hard to determine if the system is running slower than normal. Normal is something you need to define for each system, preferably in an automated way that updates your baseline over time.

Read the rest of "Baselines" at SQLServerCentral