Comment 22 for bug 568120

Thanks for intervening, Jan! I'll try your suggestion.

For the benefit of others: you can easily downgrade from the Debian package to the official Ubuntu package, as follows:

System - Administration - Synaptic Package Management

Search for hdparm and click on the installed Debian package (9.27-2)

panel Synaptic - Package - Force version...

select version 9.15-1ubuntu9
..and apply.

Then add the lines which Jan suggests, to hdparm.conf.

Then reboot. And test.... Please report your findings here.