I would like to add a Raspberry Pi to an existing two-node server setup to get an utility / playing / monitoring linux system independent from the two PCs, but I can not actually consume another mains plug.
My idea would be to power the Raspberry Pi from USB ports of both PCs so if one goes down or gets shut down the Pi will always be powered, but I know / presume I should not directly connect the power lines of the two USB ports together.
This is possibly related to this other question but I have to interface to two actual PC usb ports and not two mains power supplies: I guess I don't have the luxury to afford voltage drops from diodes.
Getting someone to do some soldering work is not a problem, as far as I tell him exactly what I need :)
Is there any ready-made product or some schematic I could use to achieve this "redundant R-Pi power supply from two USB ports" ?