linux-kernel - Re: Quick question about libata and hdparm

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Date:	Sun, 19 Apr 2009 17:27:52 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Rogério Brito <rbrito@....usp.br>
CC:	Michael Tokarev <mjt@....msk.ru>, Mark Lord <lkml@....ca>,
	linux-kernel@...r.kernel.org
Subject: Re: Quick question about libata and hdparm

Rogério Brito wrote:
> Hi, Jeff.
> 
> On Apr 19 2009, Jeff Garzik wrote:
>> Michael Tokarev wrote:
>>> Well, the kernel does a good job here in *almost* all cases.
>>> The problematic case is when a device has some bad/unreadable
>>> blocks/sectors.  When such a place occurs on read, libata
>>> (or whatever it is) performs several retries, each time
>>> using "less aggressive" settings - like reducing UDMA and
>>> PIO mode till the lowest possible PIO/33.  And the device
>>> stays in that mode until reboot, even if the problematic
>>> sector has been relocated.  So it'd be nice to be able to
>>> reset the mode back in such cases.
>> Do you have a log?
> 
> I have a log here of libata reducing UDMA speed. I don't know if this is
> any hardware problem or not (I think not), but I do see libata
> complaining and reducing the speed of the drive.

Well, it's supposed to reduce speed in several circumstances... just not 
Michael's.  :)

	Jeff



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