Archive for the ‘Jeff Szastak’ Category

Greetings Virtual Insanity readers!

My name is Jeff and I am Sr. Systems Engineer / Solutions Specialist at VMware. I specialize in virtualizing messaging systems (Microsoft Exchange, Zimbra), databases (Microsoft SQL), ESX Performance, and Security. My posts are my thoughts at the time I write them and do not reflect those of my employer. I reserve the right to change my opinion as technology evolves and I learn about new ways of getting IT done. And please test any settings described in our posts in a test environment to see if how they will impact your production environment.

I recently had a conversation with a colleague of mine regarding hyper-threading which led to this post.

Here is the question: VMware’s Performance Best Practices for vSphere whitepaper recommends enabling hyper-threading in the BIOS (see page 15), but the application vendor recommends disabling hyper-threading, can I enable hyper-threading for the ESX host while disabling hyper-threading for a specific virtual machine? Yes.

The conversation centered around Microsoft’s recommendation to disable hyper-threading for production Exchange installations and configuring a virtual machine to accommodate this recommendation.

TechNet, “Hyper-threading causes capacity planning and monitoring challenges, and as a result, the expected gain in CPU overhead is likely not justified. Hyper-threading should be disabled by default for production Exchange servers and only enabled if absolutely necessary as a temporary measure to increase CPU capacity until additional hardware can be obtained.”

So, how do I go about disabling hyper threading for a specific virtual machine while leaving the option enabled in the BIOS of the ESX host?

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