Not all Exchange Server 2007 Performance Monitor counters should be used for alert-based monitoring. But there are a few that you'll want to rely on more frequently. This tip from Microsoft Exchange Server expert Brien Posey lists three Performance Monitor counters that you should use for alerts-based monitoring of your Exchange 2007 server.
One Performance Monitor counter that shouldn't be used to automatically generate alerts is %ProcessorTime. Microsoft recommends that this counter average less than 75% to 80% usage, depending on the situation and version of Windows that you're using. Even so, it's normal for this counter to occasionally spike to 100%, which is exactly why you don't want to generate an alert every time the counter exceeds the maximum recommended value.
System/Processor Queue Length counter
The System/Processor Queue Length counter is probably the main processor-related Performance Monitor counter available. It reports the number of instructions that are waiting to be processed in the CPU queue. It's normal to have some instructions backed up in the queue, especially since the monitoring process consumes CPU cycles. Microsoft recommends that the maximum queue length be five or less.
A queue length that exceeds five doesn't necessarily indicate a problem. It just means that there are times when there is more work than the CPU can handle. The situation isn't considered problematic unless the queue length is 10 or more, which indicates an overwhelmed processor.
One caveat is that threshold values are only valid for servers with a single CPU. If a server has multiple CPUs, it will have multiple CPU queues that each must be monitored. Ideally, there should still be five or less items in the queue. However, if there are multiple queues, there may be more than five instructions waiting to be processed on a system-wide basis.
Keep in mind: This counter is also used to ensure that a system is operating efficiently. It's common for servers to use CPU affinity to assign specific applications to certain processors or processor cores. If you're using CPU affinity, you can use this counter to make certain that the server's overall workload is evenly distributed.
Memory/Available Mbytes counter
Exchange Server 2007 heavily depends on having sufficient memory. Microsoft recommends that Exchange Server always has at least 100 MB of available memory. Therefore, it's important to monitor the amount of available memory.
Note: The word available is a relative term that does not necessarily mean unused. The Available Mbytes counter lists the sum total of unused memory, zero page lists and standby memory.
Network Bandwidth counter
The Network Bandwidth counter shows the total volume of traffic passing through a network adapter at any given moment. This includes data and packet header overhead as well as non-data packets.
Assuming that an Exchange Server is using Gigabit network adapters, the total volume of traffic passing through each adapter per second should be below 70 Mbps. Higher numbers indicate that the network adapter may be overworked. If you're using Fast Ethernet adapters, the threshold value will drop to 7 Mbps.
Note: All values mentioned in this tip apply to Exchange Server 2007 running on Windows 2003. Values may differ on Windows 2008 servers.
About the author: Brien M. Posey, MCSE, is a five-time recipient of Microsoft's Most Valuable Professional (MVP) award for his work with Exchange Server, Windows Server, Internet Information Services (IIS), and File Systems and Storage. Brien has served as CIO for a nationwide chain of hospitals and was once responsible for the Department of Information Management at Fort Knox. As a freelance technical writer, Brien has written for Microsoft, TechTarget, CNET, ZDNet, MSD2D, Relevant Technologies and other technology companies. You can visit Brien's personal website at www.brienposey.com.
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