I recently turned on the side channel aware scheduler to be "security compliant". But the obvious change is that my total number of logical processors on the esxi host is cut IN HALF.
I don't know how this is an acceptable solution or a work around. Basically, if you buy a server for esxi with an intel chip, turning on side channel aware scheduler disables hyperthreading. So that's where you lose half your logical processors.
Let me show you the math.
A 12 core intel cpu server with esxi installed would have 24 logical processors available for your vm's on that host.
INSTEAD, with side channel aware scheduler turned on the same example would mean you have 12 logical processors available on your host.
This directly affects your capacity, deployment, and obviously if you have a vm that uses more than the number of logical processors you get performance hit.
This directly affects shops that purchases intel cpu's with lower core counts.
All the sales people don't explain this part, all they do is generalize the problem and say it depends on your work load.
That's BS, you lose HALF of your LOGICAL PROCESSORS, how about that.