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Performance monitoring in Windows: An overview

There are several performance monitoring tools available to Windows administrators. Which tool you use will depend on what you are trying to accomplish, your operating system and your technical skills.

It is normal for a system's performance to diminish over time as more applications, drivers, etc. are installed. Eventually though, a system's performance may reach an unacceptably low level. When this happens, you need to know what to do about the problem.

In some cases, you might simply need to replace an aging system. But in other cases, a simple memory upgrade or the removal of a buggy device driver might give the system's performance a huge boost. The problem is that Windows isn't going to come right out and tell you what you need to do to fix the problem. It's up to you to figure out which diagnostic utility to use.

There are three primary performance monitoring utilities that are included with various versions of Windows. Each has its advantages.

Performance Monitor

Performance Monitor is the primary tool for diagnosing a system's performance. It has been around since the days of Windows NT, and has had several different names along the way. You'll find some Microsoft documentation calls it PerfMon and some older Windows' versions call it System Monitor.

This tool allows the administrator to select the specific counters they want to monitor. Each counter corresponds to a specific aspect of system performance. By selecting the counters appropriate to the situation at hand, an administrator can diagnose system performance at a granular level.

Performance Monitor can not only diagnose performance problems, but also help prevent them. In many organizations, it's common practice to run Performance Monitor against the organization's servers on a constant basis.

When this is done, the counter sampling frequency is set low so that Performance Monitor only minimally impacts the server's performance. Depending on the organization, Performance Monitor can sample performance data once an hour or a few times a day.

The advantage of doing this is that the collected data can be logged and analyzed. This allows the organization to spot trends. By examining long-term Performance Monitor data, a systems administrator may learn when an organization's servers are under the most stress.

Analysis of long-term data also shows organizations how much each server's workload increases over time. This information is important for preventing performance-related problems from occurring down the road. For example, if you noticed that your server has to work 3% harder each month, you could estimate that a year from now the workload might routinely be 36% higher than it is today. With that knowledge, you can plan for any upgrades that might be necessary for the server to better handle the increased workload.

The major drawback to Performance Monitor is that there are hundreds of counters to choose from. Unless an admin understands what each counter actually measures and knows how to interpret the collected data, Performance Monitor is worthless.

Task Manager

Since using the Performance Monitor can be complicated, Microsoft built a simplified version of the Performance Monitor into the Windows Task Manager. You can access this simplified monitor by pressing Ctrl+Alt+Delete, then clicking the Task Manager button.

The Task Manager cannot perform the various logging functions that are available through the Performance Monitor, and in most versions of Windows, you cannot look up additional performance data. But what the Task Manager lacks in functionality, it makes up for in simplicity. For example, key information related to CPU, pagefile, and memory usage are clearly displayed.

Reliability and Performance Monitor

Windows Vista and Windows Server 2008 have introduced an augmented version of Performance Monitor called the Reliability and Performance Monitor. One of the tool's key features is its ability to collect event log information and use it to determine the machine's reliability. Reliability is not only based on errors, but also on factors like application or driver installation. Key events are logged on a time line so an administrator can read a machine's history at a glance.

The Reliability and Performance Monitor also includes several pre-defined data collector sets. These data collector sets frees administrators from trying to figure out which Performance Monitor counter to use (although manually selecting counters is still an option). Also, administrators no longer have to interpret graphs, as the predefined data collector sets generate reports.

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