The most effective way to optimize your server is to examine the behavior of the system while it is in operation. You can do so by using Performance Monitor. One of the most important elements of performance tuning is to maintain Performance Monitor logs. If you don't record this information, you will have no data for evaluating performance. You can set these logs to record only every two or five minutes; but this is sufficient for most performance tuning work and doesn't require a lot of storage space.
There are three major areas to watch when you are monitoring a server that has online users:
Trends in submitted loads Observe whether users are sending more messages now than they did a few months ago and whether the average message size is increasing. These factors change the load on the server, and if you are not aware of them, the load can slowly increase until you have a response-time problem. Microsoft Exchange Server provides counters that indicate the overall workload.
Service times If you monitor only the server, it is nearly impossible to calculate the actual response times that users experience. However, if you observe the server components of the response time, you can get a general idea of whether slow server response times are becoming an issue. Microsoft Exchange Server provides Performance Monitor counters that indicate server response times.
Resource use By observing the utilization of various resources, you can see where the bottleneck in a system is and even get an idea of where the next bottleneck might occur after you resolve the current bottleneck.
The following sections describe the counters of most interest to an administrator, performance analyst, or capacity planner.