Q: 20 ms latency is hardcoded?

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A: There are two sets of latency thresholds defined in the Jetstress xml configuration file: One is strict for a test short than or equal to 6 hours. The other is lenient for a test longer than 6 hours (it is also called a stress test).

 

Excerped from Jetstress chm help file --- Enables you to specify the period for performance sample gathering. If you specify less than or equal to six hours, the resulting performance log will contain six hours of performance samples. The performance test becomes a stress test when the duration is longer than six hours so that it uses a lenient set of the disk I/O latency thresholds.

 

 

The latency thresholds for Exchange 2003 still apply for Exchange 2007.

https://blogs.msdn.com/hmlee/archive/2005/07/23/442116.aspx

 

Editing these thresholds is undocumented. I guess that it is ONLY available for some corner cases.

 

- <Thresholds Name="Strict">
      <AverageDatabaseReadLatency>20</AverageDatabaseReadLatency>
      <MaximumDatabaseReadLatency>50</MaximumDatabaseReadLatency>
      <AverageLogWriteLatency>10</AverageLogWriteLatency>
      <MaximumLogWriteLatency>50</MaximumLogWriteLatency>
  </Thresholds>
- <Thresholds Name="Lenient" TestRunTypes="Stress">
      <AverageDatabaseReadLatency>20</AverageDatabaseReadLatency>
      <MaximumDatabaseReadLatency>100</MaximumDatabaseReadLatency>
      <AverageLogWriteLatency>10</AverageLogWriteLatency>
      <MaximumLogWriteLatency>100</MaximumLogWriteLatency>
  </Thresholds>

 

CAUTION: They are editable through the xml configuration file.

You have to use an extra CAUTION in editing thresholds,

since using big thresholds can break down your hardware.

 

 

Hyungmin Lee [MSFT]

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