The Dell Poweredge R720
Certainly a beast of a machine. Problem is the lack of user configuration for fan speeds. Dell seems either not to care about sysadmins and their hearing; or users tweaking their hardware.
It’s a shame, it’s a nice box and prices are reasonable for a home server.
See also: information from the UnRaid forums
Update (19-July-2019) –
Here’s a how you do it: