Comment 374 for bug 59695

Akshay Srinivasan wrote:
> So , the hard disk doesn't exactly go into suspend when the disk head is
> parked, so the kernel doesn't get to know that the disk head is
> parked(because standby=>parking) - it interprets this as a sign that the
> hard disk is in Active/Idle mode.So it doesn't bother stopping data from
> being written to the disk - this will inevitably cause the head to
> unpark from the ramp.What do you guys think of this ?I think the problem
> is associated with the way in which the standby command is issued (by
> the kernel?).My disk never went to standby on laptop-mode , just a bunch
> of head parkings.

But that's not how laptop mode works. Laptop mode simply assumes that
the drive has been configured to "do the right thing" during idle
periods, and then it simply holds off I/O as long as possible, and then
tries to cram in as much I/O as possible at a time when there is some
I/O that cannot be postponed. The kernel never actually checks the
drive's power state, just like it doesn't actively spin it dow -- it's
using only the assumption "if I hold off I/O for longer periods, the
drive will somehow use this to save power".

Cheers,
Bart