Re: Laptop mode causing writes to wrong sectors?

From: Bart Samwel
Date: Sat Nov 19 2005 - 06:13:11 EST

Vojtech Pavlik wrote:

The issue might be that these people are using

hdparm -S xxx


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.

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