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Performance data from Average Disk sec/Read counter of the PhysicalDisk performance object

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at http://go.microsoft.com/fwlink/?linkid=34707.]  

Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool includes a performance data collection engine that is used to query performance counter objects on computers that are running Exchange 2000 Server or Exchange Server 2003. The performance data collection engine collects data from the Avg. Disk sec/Read performance counter of the PhysicalDisk performance object to analyze performance data. If the Exchange Server Analyzer collects any data from the Avg. Disk sec/Read performance counter, the Exchange Server Analyzer displays information about the collected data as baseline information.

The Avg. Disk sec/Read performance counter indicates the average time, in seconds, of a read of data from the disk. The average value of the Avg. Disk sec/Read performance counter should be under 10 milliseconds. The maximum value of the Avg. Disk sec/Read performance counter should not exceed 50 milliseconds.

If you collect results from the Disk Reads/sec and Disk Writes/sec counters, you can determine whether the I/O generated by Exchange Server is increasing or decreasing over time. If you collect results from the Avg. Disk sec/Read and Avg. Disk sec/Write counters, you can determine whether storage latency has changed over time. For example, the following steps help you predict if storage throughput is or will become a bottleneck:

  1. Take measurements monthly, preferably on the same day each month and during the same hours on each day.
  2. Analyze the collected data.

By default, the Exchange Server Analyzer retrieves a sample every 30 seconds for a two-hour period. The Exchange Server Analyzer reports the maximum value for the performance counter during the collection interval. The Exchange Server Analyzer also reports the value that is at the ninetieth percentile of all collected values.

noteNote:
If you list in ascending order all the values that the Exchange Server Analyzer collected, the ninetieth percentile is the value at the ninetieth percent position in the list. The ninetieth percentile value indicates the high values of this counter during the collection interval.

In some instances, the maximum value will be the value at a peak point in the interval. Therefore the maximum value is not representative of the whole interval. The median value does not always accurately indicate load because the median value includes idle time during the collection interval. Therefore, the Exchange Server Analyzer reports the maximum value and the ninetieth percentile value.

The information in this baseline message is for information purposes only. There is no action required.

For more information about suggested thresholds of performance counters, see Troubleshooting Exchange Server 2003 Performance (http://go.microsoft.com/fwlink/?LinkId=47588).

 
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