Comment 492 for bug 59695

Just to (re?)state the obvious:

A standard Linux kernel flushes to disk every 5 seconds. I don't know what anyone expects their disk to do to "save power" between those flushes, but it doesn't. When the drive manufacturer sets default settings it is under the assumption the OS is not going to force the disk up every 5 seconds, but rather is going to make an effort to minimize disk access. If the OS knows it needs the disk every 5 seconds, it should explicitly disable APM.

Ubuntu is "at fault" (and I don't mean this offensively!) in that it allows APM to be enabled but does not enable the laptop_mode of the kernel to minimize disk access.

Sure the drive/BIOS default settings are aggressive, sure the disk wants to park after 1 second and spin down after 2 - this would be fine if Ubuntu would minimize disk access, but ANY power saving settings is unacceptable with a standard install which kicks the disk every 5 seconds. Exactly how should it save power that way ?

Without laptop-mode enabled and active there should be no APM enabled at all.

Similarly, for the following and similar quotes:

"So the ball is in the manufacturer's court in that they need to adjust the head parking idle time to something more sensible, or at least provide utilities that can allow the user to tweak the setting. Hitachi for one does not provide this ability."

Linux is forcing the disk up unconditionally every 5 seconds - there is no "sensible setting" for head parking idle time except "off"!

What am I missing that seems to make this such a complicated issue ? When not in laptop_mode, APM must be off. Period. Nothing to do with firmare or BIOS. Nothing to do with settings. Just common sense. If you kick the disk every 5 seconds, APM makes no sense. What is the disk going to do to save power?