When someone experiences a performance comparison issue when a workload is moved from physical to virtual (or from another virtual platform/system) this is how I approach diagnosing it or identifying why performance was different.
Let me start by saying that using current infrastructure and the latest versions of vSphere, there should be little or no performance difference between physical and virtual. Very rarely is a true issue or an incompatible application identified. The most common reason people see an issue with comparisons is a result of the following:
- A poorly conceived performance test
- A mis-configuration within the hardware/software stack
- Hardware differences between the tests
While this might seem obvious, it happens far too frequently in my experience. As a result, I approach these situations by doing two things. First, explain and encourage the adoption of my golden rules for comparisons. Secondly, use the cheat sheet below to document details in the environment which usually bubbles up some sort of difference.
Here are my golden rules for performance comparisons:
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