There's different takes on it, that's just mine. I really appreciate and respect their work.
That’s a mainframe, sport. At their height they were modular and in at least IBM’s case they could run with damaged parts and were delivered with dark hardware that could replace damaged parts until a maintenance person could arrive, or be remotely enabled to increase throughput for a fee.
All of this cloud stuff, except the geographical redundancy parts, is recreating software that business had versions of forty years ago.
(While the rack is the unit of delivery overall, we can ship individual sleds and they’re operator replaceable, if say, one of your sleds dies, incidentally.)
The old machine was about desk height and 15 feet wide. The new machine was a 4u box running a Unisys mainframe emulator on NT 4, on a quad processor pentium pro. Pretty sad. But they did keep the giant line printer, at least while I was working there.
Hyperscaler rack designs definitely blur this line further. In some ways I think Oxide is trying to reinvent the mainframe, in a world where the suppliers got too much leverage and started getting uppity.