External HD Operation

I have a setup with an external USB hard drive as PRIMARY. The HD is self-powered and is always on. Is the external USB hard drive always spinning or does the aTV Flash/Apple TV spin down the external USB hard drive when not in use? I do not use the Apple TV all of the time and I’m concerned with the hard drive spinning 24/7.

If the hard drive spinning is not controlled by the aTV Flash/Apple TV, can I connect the external hard drive power cord to the switched outlet on my AV Receiver? The Apple TV HDMI is connected to the AV Receiver, so I cannot use the Apple TV unless the AV Receiver is on. In this case, when I want to use the Apple TV (via an Activity on a Harmony remote), the receiver is turned on which in turn would power the external hard drive and start the Apple TV. If need be, I can set up the Harmony to turn the AV Receiver on first.