I mentioned this on another thread but it wasn't main topic there. I have an HDD in an enclosure connected to Raspberry.
While connected to USB 3.0, the drive is spinning (but no reads/writes), kill-a-watt shows power consumption of 5 watts. Then the drive spins down instead of going down, power consumption goes up to 5.4 watts. I checked few different enclosures and the same thing happens on all of them.
While on USB 2.0, power consumption goes down as one would expect.
Power consumption without any USB device connected is 3.5 watts (after VLI firmware update).
If these 2 watts don't go into the drive as it is spun down, I wonder what is being heated.
Can some Raspberry Pi engineers look into this? It shouldn't be hard to confirm this issue.
edit: I will leave Raspberry on idle with HDD spun down and see tomorrow if the controller or the drive itself is warm/hot