In order to effectively monitor current utilization and plan for future growth for MS Exchange servers, various performance metrics can be tracked; some of which should be monitored in real-time and others should be stored for historical analysis.

Real time Monitoring - The following can be monitored using NT's Perfmon facility, or any other commercially available monitoring product (eg. Metron's NT Monitor or Critical Services Monitor):

• Processor: % Processor Time
• Memory: Available Bytes
• Physical Disk: Percentage Disk Time
• Physical Disk: Disk Queue Length

Monitoring these metrics in real-time will give you a view of the critical hardware resources. It lso provides an excellent indicator of the overall system performance of your Exchange server.

Historical Monitoring - In addition to real-time monitor information, Exchange administrators need a performance database (PDB) for problem solving and historical trending. The administrators need the data organized and placed in a PDB because massive amounts of performance data from many mail servers are generated on a daily basis. This data can then be used to create a baseline of current usage patterns. After baselines are created, analyzing the data will reveal any bottlenecks. The data can be used to determine when to upgrade the system or modify any system configuration parameters.

As a minimum, the following metrics should be tracked over time using the PDB:

• Processor: % User Time and % Privilege Time;
• Memory: Available bytes, Paging/Second, Available Physical Memory Bytes and System Cache Bytes;
• Physical Disk: Percentage Disk Time, Disk Queue Length;
• Logical Disk: Percentage Disk Time, Disk Queue Length;
• System objects: System Calls and Context Switches Per Second, System Processor Queue Length;

These metrics show the Operating System metrics that should be collected, and a number of third party monitoring tools (eg. Metron's Athene) also allow the collection of metrics that are specific to MS Exchange. If such a tool is in use, then these can be combined with the O/S metrics above to generate a detailed view of Exchange's performance.