Re: Laptop mode causing writes to wrong sectors?

[Bart Samwel <bart@samwel.tk>]

Vojtech Pavlik wrote:

> The issue might be that these people are using
>
> 	hdparm -S xxx
> 	
> 	or
>
> 	hdparm -y / -Y
>
> while a much better way to do
>
> 	hdparm -B 63
>
> The -S option should in theory be safe, but I remember some drives did
> behave unpredictably if this was used.

Well, some drives have a specific lower limit on the -S values that are 
supported. That's the only compatibility problem I've ever encountered 
with -S. (And you can find out if a drive has a lower limit by checking 
hdparm -i.)

> -y/-Y is much tougher and some
> drives will not work reliably unless first woken up manually before
> issuing a read/write request.

In fact, -Y is problematic but -y usually isn't. -Y puts the drive to 
sleep and requires that Linux reset the complete IDE controller before 
using it again, while -y simply puts the drive in standby mode, leaving 
it up to the drive to decide when it spins up. I've never heard of any 
problems with -y.

> On the other hand, -B is pretty safe on drives that support it, and all
> IBM notebook drives do.

Not true, unfortunately. In fact, I had to change the default config of 
laptop-mode-tools a while ago so that it wouldn't use -B, as it seemed 
to be one of the *causes* of hangup/corruption problems. This was also 
an issue on Thinkpads, and I think it was also noted in the ubuntu bug I 
linked to earlier.

An additional problem is that the values for -B are not really 
standardized, while the values for -S are.

--Bart
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