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VDI Performance Testing: To VSImax or not to VSImax

VDI Performance Testing: To VSImax or not to VSImax

When you are performing a VDI performance test with Login VSI, the most important part of any test are the results. But the result is only valid when you have completed a successful test, because there are many factors that can influence the test result. So how to make sure that a test was run successfully? One of the misconceptions that I hear quite often is that fact that you will need to reach VSImax for a test to be considered successful. In this blog I will explain the best way to determine if a test was successful or not.

To VSImax or not to VSImax

Some of our users have the idea that if you run a test with Login VSI and you have not hit VSImax, it’s not a good test. And I understand where that comes from because that has also been a little bit our own fault by releasing benchmark reports like Project VRC, #VDILIKEAPRO and many of the validated and certified reports from our vendor community, but this was actually never our intention. If you don’t hit VSImax, it basically just means that you ran all of these sessions with no problems and that you never reached the maximum capacity.

So if you have an environment with a thousand users and you just want to know if you can support those thousand users, and you don’t hit VSImax, that means that you can actually support 1000+ users, which is a good thing right? If 1000 users is all you need, you could stop there but if you really want to know how much your environment can support, you will need to push it a bit more. Plus most guys want to see how fast things go so it’s also more fun to hit VSImax :-).

Let’s compare this situation to a car. If you drive a Ferrari and you only drive it 100 km / 65 miles per hour, you will never know what its true performance is. So if you really want to know what its true capabilities are, you will need to go full throttle. The same applies to VDI.

A successful test? That’s the question

So it’s up to you to decide if you want to hit VSImax or not, but hitting VSImax definitely doesn’t determine if a test has been successful. But how can you determine if a test was successful? There is an easy way to check this in the Login VSI Analyzer.

After opening test results, people usually click to the famous VSImax chart in the second tab of the Login VSI Analyzer and they completely ignore the first “Summary” tab. But this information is very important to understand the success of your tests.

login vsi analyzer test summary

Summary tab in the Login VSI Analyzer

If you look at these results it will immediately tell you if the test has been successfully completed or not. Plus it will also tell you if you had too many problems such as:

  • Number of sessions that were configured to be launched in amount of seconds
  • Number of sessions that failed during the test before VSImax was reached
  • Number of sessions that were not successfully launched
  • Number of launched sessions failed to become active
  • Number of sessions that were active during the test
  • Number of sessions that got stuck during the test (before VSImax threshold)

This report will also tell you the percentage of configured sessions that are higher than VSImax. If this percentage it too high, we recommend to run another test with fewer users because this might have a positive effect on VSImax.
So after running any test with Login VSI, please always make sure to first check the summary tab to make sure that you executed a successful test before drawing any conclusions by looking at the VSImax chart.

Ps. If you would like to know more about VSImax, my colleague Jordi wrote an excellent blog about how VSImax is actually calculated.

About the author

Mark Plettenberg (@markplettenberg) is a product manager of Login VSI and has played a critical role in the development and growth of Login VSI. Ask Mark about motorcycle mechanics and breaking/repairing anything and everything that has a power plug.


Tags: Login VSI, Load Testing, Best Practices, VSImax, Support

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