In the VCP series Don suggests that you typically do not enable Hyperthreading.
I am having a hard time finding any official documentation that supports this idea.
Would you be able to share documents that might help me decide if Hyperthreading is right for my HOSTS?
Long-time supporter and loving the content.
-
ESXi 5.5 and Hyperthreading
-
@danny-perry Sorry for the super-late delay in answering this question. I could have sworn I already answered it, but Ronnie pointed it out to me this morning.
Anyhow, the answer to your question is that Hyperthreading can create unreliable performance results. Sometimes you have the speed, and sometimes you don't. VMware's official stance is this:
An ESX/ESXi host enabled for hyperthreading should behave similarly to a host without hyperthreading. You might need to consider certain factors if you enable hyperthreading, however.
The example they give is:
Consider your resource management needs before you enable CPU affinity on hosts using hyperthreading. For example, if you bind a high priority virtual machine to CPU 0 and another high priority virtual machine to CPU 1, the two virtual machines have to share the same physical core. In this case, it can be impossible to meet the resource demands of these virtual machines.
You can read the full writeup in VMware's Resource Management Guide available here: Hyperthreading and ESX/ESXi Hosts.
At the end of the day, Hyperthreading sometimes creates a performance benefit, but it always creates a performance risk as it might not be available when you need it. As a result, I recommend disabling it so that I always have reliable performance numbers. If you have 4 cores, but need 8 then you should upgrade to 8 cores instead of activating Hyperthreading.
Hope that helps, and again, sorry for the insane delay in answering.
Don Pezet
Host, ITProTV
