I have a set of external disks I use for backup purposes for my Plex box. In their next to second final state, where I setup something to turn them on and off with a script, I have them wired to a xbox 360 power supply and a 10 port powered usb hub. The hard drives connect to the hub, the hub to the server. As you do. The fun part, the hub isolates power to the devices from the host pc so I can simply turn off power to the hub and the usb things disconnect.