I'm buying a NAS and im going to get the i3 4160 its a 2 core processor with hyperthreading. I want to setup some jails so will I be able to run a jail with 2 cores and it will still have a 2 on the NAS? or will I only be able to use 1?
As far as i know virtualization gets handled by the host as as incomming threads.
But with a core i3 with only 2 physical cores im not realy sure if that would be realy ideal in this case.
Like MisteryAngel said the redirection of instructions into cores or thread is done automatically. If you're running a light OS in said jail I guess you can get away with two threads (headless machine are best suited for low power machines, in this case the jail you want to use).
From VirtualBox and QEMU a dual core HT Intel CPU can be seen as 4 cores in a VM but inside the VM you will never see the cores pass 50% utilisation with with tools. While the host is 100% maxing out the 2 cores.
So yes VM count HT cores but use wisely as there not really cores in the VM