Recently visiting a small data room, I noticed that redundant power supplies of a server are connected through a C14 splitter which, in turn, is connected to a single socket of a UPS.
I told the person who was showing me the data room that in my humble opinion, this makes no sense: if one has only one UPS, then only one of the two PSU should be connected. He replied that with redundant PSUs, it is always better to connect both PSUs, even through a splitter; doing otherwise, i.e. connecting only one, would create unnecessary stress on the connected PSU.
What is this stress thing? Isn't the first PSU doing all the work anyway in an ordinary configuration where both PSUs are connected, the other one being used only when the first one fails or is disconnected?