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Using Virtual Machines as Load Generators

Hi All,

We would like to know the feasibility of using a virtual machine as load generator. We received a document from HP stating that it is not advisable to use VM machines as load agents. In one of our requirements, we have virtual machines hosted in Red Hat Linux box and the operating system of VM is Windows 2003 server; QUAD Processors; 8GB of RAM. If we execute a test run with VM as load agent, what are the possible errors/issues we will be facing?

Thanks,
Ramya
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The most common reason for which virtual machines are not recommended is that the response time obtained in the load test using virtual machines will not be the same as the response times you would obtain in a normal setup. This would mean that your load test results are not showing the actual performance of the application as opposed to what it would be in the real world.

Thanks
Prashanth T
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Thanks Prashanth. Apart from response time, wil there be anyother factors that might affect the final result of the execution. We need to have more than one factor to go aginast or for it.

Thanks,
Ramya
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I don't agree with the theory that response times will be affected simply due to the fact that the machine is virtualized. After all, many production environments are running on ESX virtual servers successfully.

I have been running Controllers and Load Generators on virtual machines successfully for several years. Frankly, I am quite suprised that HP would put together a document specifically discouraging the practice - especially this is not reflected in the documentation of prerequisites.
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Thanks James. But we do have the documentation for LR9.50 with us in which HP has clearly mentioned that "It is not recommended to run Load Generator for load testing purposes on Virtual Environment". Now we are in a position to justify the client that we can run on virtual machines. But we dont have a foolproof statement/result to justify them. If anyone has any kind of documentation shared by HP in which virtualization is supported, please do share it with me.

P.S:I have attached the PAM document shared by HP in which the above statement is being mentioned.
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This recommendation could be due to fact that VM ware does not use hardware for the clock (relative system time).

I guess VMWare's technology has some issues regarding the accuracy of the system clock that the OS uses for time management.

May be you will have to wait for some more time to hear from other LIVE experts running VMware LoadAgents.

I suggest you to contact HP support and check their suggestion.....

btw....LR PAM should be not shared in the public forum, as this is confidential document....accessible to only HP & partners.

~Shivaram
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Thanks. When raised this with HP, they replied back stating that the VMware's clock does not synchronize with the hardware clock. This causes inaccuracy in the response time obtained.
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Thanks a lot for your responses.
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Mark Tomlinson, the Product Manager of LoadRunner, has a video blog about this: http://www.communities.hp.com/online/blogs/loadrunner/archive/2009/09/05/109408.aspx
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