On Tue, 2020-12-01 at 12:06 -0800, Samuel Sieb wrote:
On 12/1/20 8:42 AM, Patrick O'Callaghan wrote:
> On Tue, 2020-12-01 at 09:01 -0700, Chris Murphy wrote:
> > On Tue, Dec 1, 2020 at 6:59 AM Tom Horsley <horsley1953(a)gmail.com>
wrote:
> > >
> > > On Tue, 1 Dec 2020 14:52:21 +0100
> > > Roberto Ragusa wrote:
> > >
> > > > How do you power them down?
> > >
> > > I don't know about the original poster, but my "noauto"
disks
> > > timeout and power down all by themselves, then even when they aren't
> > > mounted at all, every time I reboot, the reboot hangs while it
> > > spins up the disks for some reason. I constantly wish I could make
> > > it stop doing that.
> >
> > Enumeration. I'm not sure if it's udev scanning everything, or the
> > kernel or both. And also maybe libblkid, to know what everything is.
> > The only way it can know what it is, it needs to be spun up to read
> > the partition map and all the signatures on each partition.
>
> Obviously it needs to spin up if it needs to know these things. My
> point is that it doesn't need to know them until I tell it.
But it can't know that it shouldn't until it knows what's there. :-)
The kernel scanning the USB bus will trigger the dock to check the
drives which will spin them up. Even if the dock didn't, the kernel
would still check the drives, so they would still be started.
OK, I can see that it's the scan that's the root of the problem.
poc