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LoadRunner – What you need to know before running on a Virtual Environment

LoadRunner – What you need to know before running on a Virtual Environment post image

“Paranoia is knowing all the facts.” Woody Allen

Can LoadRunner or performance center run on a VM?

The question is not whether or not you can run LoadRunner components in a VM, but rather, should you? It’s a debate that has been going on at my company for quite some time. Some advocates only physical machines, while others swear by all things VM. Who is right? Who is wrong? Depending on the components, they may both be right.

Vugen

Since all you’re doing with Vugen is developing scripts, you should be able to use it within VM without issues.

Load Generator

The Load Generator component of LoadRunner is very sensitive to timing issues that sometime occur in a virtual environment.

The reason for this is that in a VM environment (based on what I’ve read on HP knowledge base KM752992) is that there have been issues with the accuracy of the system clock that’s used for time management. On a physical box, the OS can use the hardware clock cycles to figure out (relative) system time. But when using a VM, the CPU cycles used are in accordance with its management of system resources.

As a result, there is potential for the accuracy/precession of time measurements (like transaction response time) to be reduced. VMware has a good tech paper “Timekeeping in the VMWare Virtual Machines” that explains this behavior in more detail, and gives some ways in which the issue can be minimized.

Bottom line: if you really need millisecond levels of precision in your test, it’s recommended that you use a physical machine.

The Controller

The controller can usually be run on a VM without any issues. I’ve read of instances, however, when there have been timing issues with timestamp offsets. The issue we talked about with accurate timing in the load generator section applies to the LR Controller as well.

I wouldn’t worry, however, about the performance measurements reported by a guest operating system running inside a virtual machine. The VM OS measurements should be “just as accurate as when the operating system is running on physical hardware. However, you must interpret these results with care, because the guest operating system does not have the full picture of what is happening on the OS.” (Timekeeping in the VMWare Virtual Machines).

The Analysis

As with Vugen, you should be able to implement the Analysis piece within a virtual environment without issues.

Servers for Performance Center

The performance center components like the File, Database servers and the User and Admin Sites can all run in a VM without any funky known issues.

Main concern — Paranoia

Maybe I’m paranoid, but honestly, my biggest concern about using LoadRunner in a virtual environment is making sure I’m not violating any of HP’s crazy licensing policies.

My company does strict licensing audits, and I’d be in pretty big trouble if I was caught violating any licensing agreements. So, for me it’s almost safer and avoids possible headaches to just use physical machines. J

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