I have a problem with my Ubuntu 15.10 amd64 system on my ASUS R513C laptop.
I am setting the APM level on my HDD to 254 by running sudo hdparm -B 254 /dev/sda by hand and this fixes a problem with the disk constantly spinning up and down every couple of seconds.
But this setting is not conserved after the computer wakes up from sleep or reboots. It is then always reset to 1, and the spinning up and down starts again.
I checked: /etc/apm/event.d/20hdparm and /etc/default/acpi-support but I can't find where it sets the -B parameter.
I've also read https://wiki.ubuntu.com/PowerManagement but didn't find a solution there.