I'm using a simple USB to Sata/IDE adapter to connect a sata drive to Raspberry Pi2 running OSMC. (the adapter you can get on ebay for a couple of dollars)
When I have a 2.5" laptop HDD connected, I can spin it down with no issues using
sudo hdparm -y /dev/sda
or
sudo hdparm -Y /dev/sda
BUT, when I have a 3.5" PC HDD connected, I can't get it to spin down. still getting the proper respond:
sudo hdparm -Y /dev/sda
/dev/sda:
issuing sleep command
but the HDD won't spin down! for the sake of it, I have also tried with hd-idle and sdparm (for reference - I used this manual)
(btw Power is from an external power supply)
Actually, I was really surprised when the 2.5" drive did spun down, because I'm really trying to get the 3.5" to spin down, and I was thinking that the usb to sata adapter wasn't sending the spindown command properly to the drive. (not translating it correctly from USB to SATA.
kind of lost here!