Allegedly, on or about 7 December 2017, Fulko Hew sent:
To disable the Advanced Power Management and to stop the head unload/clicking I've always used:
hdparm -B 255 /dev/sda
But on this machine/drive, it doesn't seem to work; or at least it only works for a short while, and then it starts unloading again.
Is this "short while" in the middle of an active session, or have you suspended/hibernated/rebooted/powered-down, in the meantime?
You may need to look into your power-management settings, and make sure that any wake-up/thaw events reprogram the setting. I had to do that with mine.
More importantly, the next time I try to disable it,it says its disabled, but the drive carries on clicking, and the Load_Cycle_Count still keeps going up.
Try a different value, such as 254, instead.