Seagate 4TB 3.5.$ hdparm -S60 /dev/sdaOK. 5 mins after no access on HDD, it spins down. No problem. But every 30 mins it wakes up by itself without any event, and goes to bed immediately. I have to wake up in the middle of night because of its spinning up sound.
hdparm -S60 /dev/sda (Works fine, but every 30 mins HDD wakes up and spins down even though not in use.)
sleep;hdparm