The server computer is running mc in server mode. The other computers are running mc in client mode.
Here is the results of some tests I've run. This is with both server and client computers turned on but not being actively used.
When the client has the option "auto sync with library" enabled, the server drives spin down but spin back up every hour or so.
When the client has the option "auto sync with library" disabled, the server drives spin down and stay down until the client tries to access the server by watch a movie for example. This setting would work except that the "watched" check marks for tv series end up disappearing when that client has to restart for whatever reason.