Dear all,
Thanks for taking the time. New to the forum and to VMs. I have read up as much as I can before posting but are not 100% sure of the answer to my question. I know with old Intel processors, hyperthreading is recommended to be disabled. On ESX with newer intels (nehalem and newer), the best practise recommends hyperthreading to be enabled.
However, this question is for the free VMware server, which only allows 2 vCPUs per VM. My quad core xeon 3460 is showing 8 logical CPUs in task manager under windows 2003 R2. This makes sense since it is 4 cores x 2 hyperthreads = 8 logical CPUs. So now, if I run a VM and assigned 2 vCPUs to it, am I just using 1 physical core since hypertheading is enabled? In other words, the 2 hyperthreads in 1 core counts as 2 logical cpus, which are then assigned as 2 vCPUs to the VM. Is this how I should look at it?
On the other hand, if I disable hyperthreading, then the host will simply has 4 cores (translate to 4 logical cpus since no HT). Then if I assign 2 vCPU to the same VM, would the VM be using 2 physical cores now? Would this be more efficient ?
Recap:
option 1) Quad core, HT enabled = 8 logical CPUs. Assign 2 to a single VM. Using only 1 core physically.
option 2) Quad core, HT disabled = 4 logical CPUs. Assign 2 to a single VM. Using 2 cores physically.
Which will give faster performance on the VM? I am thinking option 2 since the VM will be using 2 cores physically, instead of 2 HTs on a single core in option 1. Or am I just not looking at this properly?
Thank you again for your time. Please shine some light to a newbie question.