You can try 2 things, to see if any one works for you.
- You can put your HDD to sleep before you power off your box. To do this you need to put these lines in autostart.sh https://pastebin.com/raw/1vhRT1tk
#!/bin/sh
(sleep 60;
hdparm -S 60 /dev/sda1
)&
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This will put your HDD to sleep (stop turning) after 10 minutes of inactivity.
- You can try to disconnect your HDD and turn it off using shatdown.sh. To do this you need to put these lines “https://pastebin.com/raw/ypmbcrEu” in shatdown.sh → Read about this method here