Tuesday, September 13, 2011

You can't make your Exchange 2010 Jetstress tests to pass

If you're testing your disk subsystem for Exchange 2010 with Jetstress and you're unable to make it "green" pass because database read latency is higher than 20 msec than it's time for reducing number of threads and for fine tuning. But, if you reduce number of threads than you will lose number of IOPS.
For example: with 2 threads you can't achieve required number of IOPS and with 3 threads you're achieving number of IOPS but database read latencies are higher than 20 msecs, in that case you can use "SluggishSessions" parameter. You can find this parameter in JetstressConfig.xml file. By default this parameter is set to 1, you can start increasing this number by 1, which will make Jetstress to add pause between tasks. With increasing "SluggishSessions" parameter you will lose IOPS.

For example : with thread count 3 and SluggishSession 2, I was able to achieve required number of IOPS but database read latencies were still higher than 20msec:

So with increasing number of SluggishSessions to 3 I was loosing IOPS but database read latencies were lower than 20 msec:

For more on threads and "SlugishSessions" check the following Technet article : http://technet.microsoft.com/en-us/library/ff459238.aspx

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