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SubjectRe: Question about IDE disk shutdown
Hi,

> Probably a trivial question for ones who know it - what IDE commands does
> kernel issue when shutting down (which results in automatic power-off if ACPI
> is enabled)?
>
> According to my hard disk manual, it is absolutely recommended to put the
> drive in STANDBY or SLEEP mode before power cut-off because in that way heads
> are nicely parked. In that way it is guaranteed to have 300000 head
> load/unload cycles minimum, while in other case it is just 20000 cycles.
>
> It also explicitely states that FLUSH CACHE is not to be used for drive
> power-off because it does not park the heads.
>
> Looking at the source I see in ide-disk.c:
>
> .gen_driver = {
> .shutdown = ide_device_shutdown,
> },
>
> Following that I see that ide_device_shutdown flushes the cache, and then
> calls dev->bus->suspend(dev, PM_SUSPEND_STANDBY); which is in fact
> generic_ide_suspend, right? There, something called REQ_PM_SUSPEND is issued
> to the drive. As SUSPEND != STANDBY or SLEEP, I am left uncertain.
>
> Is there a place to be worried or I am missing something?

This kind of thing has been discussed extensively in the past. Basically,
there are loads of broken drives which do a wide range of different things,
so following the standards doesn't necessarily work best in practice.

John.
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