Customizing Jetstress

Recently, a few folks asked me about changing the Jetstress default behaviors. In other words, they wanted to customize Jetstress one way or another. It is actually quite easy to do that. Jetstress uses an XML file as its configuration file. All you need to do is to modify that configuration XML file and save your changes. Let me show you some examples below.


Test Duration




The default value is 2H, or two hours. If you want to run the test for 24 hours, you would modify the value to 1D. If you want to run the test for a week, use 7D; and the modified XML tag would look like this: <Duration>P0Y0M7DT0H0M0S</Duration>.


Note that as you run the test longer and longer, the database will grow larger and larger. So, you need to keep an eye on the disk space and avoid the disk full situation.


No Checksum Verification




The default value is true, or verify checksum after a Jetstress performance or stress test. The checksum verification will scan the databases and catch and report data corruption error if there is any. However, the process is time consuming. If you need to run the tests repeatedly in the lab, you can opt to disable checksum verification by change the value to false: <VerifyChecksum>false</VerifyChecksum>.



Output File Location




The default path is the directory where Jetstress was installed. Normally, that path is “C:\Program Files\Exchange Jetstress”. What I usually do is to create a sub-directory “C:\Program Files\Exchange Jetstress\results” for all the output files. So, the modified tag becomes: <OutputPath>.\results</OutputPath>


Thread Granularity




As you know, thread count is an integer. When you increase the thread count, you tell Jetstress to generate more IOPS per database. But what if your desired IOPS falls between n and n+1 threads?


The tag SluggishSessions allow you to do some fine tuning. The default value for SluggishSessions is 1. Increasing this value will give your more granularity; or fewer IOPS generated by each thread. Most likely, you only need to set this value to 2, i.e., <SluggishSessions>2</SluggishSessions>. And it’ll take some experimentation to find out the exact thread count for the IOPS you try to target. 


What not to Change


One thing you don’t want to change is the Jetstress IO pattern, which is governed by the following tag:


<OperationMix LockOps="true" InsertOps="40" DeleteOps="20" ReplaceOps="5" LazyCommits="70" />.


However, if you really want to change OperationMix, you better have a very good reason.


Given the fact that XML files are easy to edit and change, it is also easy to introduce unwanted changes inadvertently; thus cause a lot of headache. So, it’s a good idea to save a copy before you make changes.


Thanks for reading. 



Can we change the default Database Caching size in Jetstress. Default caching size is Min:32MB Max:256. I want to change it. How to change the Database Maximum/Minimum Cache size in Jetstress 2010

lwei Former NetApp Employee

I don't think you can change that parameter. Why do you want to change it?