On Sun, Dec 10, 2017 at 12:32 AM, Tim <ignored_mailbox@yahoo.com.au> wrote:
Allegedly, on or about 7 December 2017, Fulko Hew sent:
> 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.

It sounds like it does work, but something else is changing the
settings on you later on.

I don't think you've said how long your change works for.

​Well, I'm not too sure.  Right now it feels intermittent
and unrepeatable, at least with a value of 255 and/or 254.
And I've tried using a 60 second interval 'touch' with those values.
Some times the touch prevents the unload/load,and sometimes it doesn't.
Again, I need to attempt a scientific analysis.

Today I've been trying 253 with the 60 second 'touch', and that HAS
worked for 24 hours, so I declare that my official workaround
(pending better test results).
I don't recall you saying what desktop you use.  It may help people
narrow down what might be periodically undoing your setting.

​I use KDE, but there may be a few Gnome utilities/apps also installed.
​(And this is Fedora 26)