Cores and threads

[awediohead]

At the moment my unraid install is based on an i5 4690k @ 3.5Ghz with four cores - it's not multi-threaded. For every day media server duties it does the job perfectly well, running numerous docker containers including Plex and performing NAS SMB sharing duties with all cores around 20% typically with a single core occasionally going 'red' at 100% briefly, though which core goes to 100% seems random. I think it would be a bit much to expect it to do more, like run a VM at the same time. Don't get me wrong, I think it could technically do it, but not do it well without doing other stuff badly.

 

But I've been watching videos where people assign 'x' numbers of cores to a VM and I wanted to better understand the nature of a core capable of hyperthreading and one that isn't and how this applies in terms of virtualisation vs bare metal.

 

For example how similar would assigning 2 cores, 4 threads of a modern multi core CPU running a VM be to running the same OS, bare metal on  4 cores (not multi-threaded)  in terms of performance? Is a non multi-threaded core the same as a thread on a multi-threaded CPU core? What's the difference?

 

To take a real world example - I have an x570 & Ryzen 3600x PC with 6 cores and 12 threads - would assigning or reserving 2 of its cores (4 threads) be roughly comparable to my i5 4690k 4 core, 4 thread CPU? Or maybe the question is better phrased, 'What's in a core that isn't in a thread' ?