Re: [patch] My AMD IDE driver, v2.7

Vojtech Pavlik
2002-03-19T21:56:38Z

On Tue, Mar 19, 2002 at 10:21:30PM +0100, Pavel Machek wrote:
> Hi!
>
> > > > commands. With the proper sequencing, you can even do power management
> > > > of the drives in userspace. You don't want to do system suspend/resume
> > > > that way, but you can certainly have a userspace policy daemon running,
> > > > that powers-down and powers-up the drives, etc.
> > >
> > > See noflushd, Hdparm is able to powersave disks well, already, and it
> > > was in 2.2.X, too.
> >
> > Not all of them safely, though. Many a drive will corrupt data if it
> > receives a command when not spinned up. You need to issue a wake command
> > first, which hdparm doesn't, it just leaves it to the kernel to issue a
> > read command or whatever to wake the drive ...
>
> Is this common disk bug, or are they permitted to behave like that?

This behavior is permitted by the specification, as far as I know -
results of commands other than wakeup (and other pm commands) in sleep
or suspend mode are undefined ...

--
Vojtech Pavlik
SuSE Labs