I have just begun watching the VCP-DCV6 training videos and in part one of the "Installing the Hypervisor", Don mentions that hyperthreading should "not" be enabled in the BIOS of your ESXi host servers. I understood his explanation, but have yet to find anything that corroborates those sentiments.
I even contacted VMware today and got this in response:
I am Namratha and am assuming the ownership of the service request ############
**Based on the case description I understand that you want to verify if ESXi 5.5 needs hyperthreading enabled. (He misunderstood my question regarding the "needing" part)
VMware recommends hyperthreading to be kept enabled on the host, because it can increase performance by better utilizing idle resources leading to greater throughput for certain important workload types.
Kindly refer the following link for more information regarding hyperthreading:
We haven't received any cases till now where there was erroneous performance because hyperthreading was enabled.
**If you have any documentation stating the above, I would request you to kindly share it with me so that I can look into it.
I hope I have answered your queries.
Please feel free to contact me in case of any further clarifications.******
The article that Don links to referencing the "no hyperthreading" recommendation is from 2013. Perhaps this is no longer an issue with more modern processors? Doesn't this KB link state that you should be careful using "CPU Affinity" when hyperthreading is enabled? That's a very specific configuration, not a default one...."right?"
Perhaps I misunderstood Don and he meant to only disable hyperthreading on older CPUs.
UPDATE: I received an update from VMware referencing the KB article that Don linked to in the "Installation of Hypervisor pt. 1" course.
Thank you for the update.
I looked into that article you sent, and as you said this is if you set the CPU affinity in an incorrect manner, thereby overburdening one core and leading to resource contention.**
Under normal circumstances, enabling hyperthreading shouldnt cause any such issues.
Please let me know if you have any further queries.