I was thinking about how I would build myself a server with redundant power supplies.

Now they sell redundant PSU units, but they are proprietary. If one PSU in the unit fails and you want to replace it you have to buy a replacement PSU that unit supports.

Do they make motherboards that have two PSU connections- the idea being you plug any two PSU into the motherboard and when one fails the mobo will intelligently switch over to the other.

I couldn't find any that do this which makes me think there is something inherently bad/unrealistic about this idea.