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Tuesday, September 23, 2008

Software testing in a virtual environment

Q- What is the likelihood of capturing accurate load testing results in a virtual test environment? We use LoadRunner/PerformanceCenter for performance testing. Our company is in the process of making use of virtualization. It seems this may be ideal for functional test environments, but not for performance test environment. What is your opinion?

A- There are a lot of ways to use virtual environments in your performance testing, so there's no easy answer to this question. I'm assuming that you're referring to hosting the entire application in a virtual environment and running your performance testing against that platform. My answer is that, as always, it depends.
Some research on the topic has found that virtual environments don't scale as well as non-virtual environments. In a study by BlueLock, a company that provides IT infrastructure as a service, they found that "the number of simultaneous users that could be handled by the virtualized server was 14% lower than the number of simultaneous users being handled by the traditional server configuration."
This is consistent with my experience testing financial service applications in virtual environments. If you don't have much choice, or if you have a lot of pressure to make it work, I would recommend that you perform a comparison performance test to prove out the new platform. If you can do that successfully, you'll have some confidence that the platform is comparable. But just be aware that over time, as the application changes and the server configurations change (both virtual and the physical servers in production) your comparison will become outdated. It may happen faster than you might think.
By Mike Kelly

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