Linux

That's a good point about what the OS provides. I come from an embedded context, so often RTOS are not much more than a kernel that's handling some basic threads and processor access. There was a really interesting talk at USENIX a few years ago (Usenix 21 keynote with Timothy Roscoe, I just looked it up) that was basically saying that a modern OS like linux, isn't even accessing hardware and is just an OS in a system of OSs on a computer.

So you are not wrong about what you are calling bare metal, but that usage is more popular at the moment, but the older meaning of bare metal actually just means "no OS." It's still very common in embedded world. They are the same words, but do have different meanings.

I cannot find it at the moment, but about 10 years ago I had found a guy at Tufts (I think) who was publishing about actual bare metal (no os) single process machines that would run a server with nothing else. It was supposed to be helpful for security reasons. It was definitely whacky. I cannot find it because the server-farm usage of bare metal has taken over :(

[Bare-Metal (redirect on wiki)[ https://en.wikipedia.org/wiki/Bare_metal ]

I do now see that "bare metal server" is not going to be the right search term. Perhaps bare metal computing? I'm not sure. But what I am talking about pre-dates virtualization.

Edit: For servers, it seems the papers are calling it "Bare PC" Example: https://doi.org/10.1109/HPCC.2009.34

The other advantage of a bare metal server is that the computing resources are guaranteed to actually be there when you need them. VM Providers are known to overbook their physical computing resources, so if other customers happen to use more compute than anticipated then your VMs mysteriously won't have the performance you paid for.

There's also a computational cost to virtualization itself, so you can add slightly more performance to a single server before you have to use a distributed system, but I doubt that's significant for more than a handful of businesses.