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

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Message-ID: <49EB1FB3.5000609@garzik.org>
Date:	Sun, 19 Apr 2009 08:57:23 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Michael Tokarev <mjt@....msk.ru>
CC:	Mark Lord <lkml@....ca>,
	Rogério Brito <rbrito@....usp.br>,
	linux-kernel@...r.kernel.org
Subject: Re: Quick question about libata and hdparm

Michael Tokarev wrote:
> Mark Lord wrote:
> []
>> Nearly all of the hdparm flags work fine with libata and SATA/PATA 
>> drives.
>> Among the *very few* that do not, are the -m and -d flags.  -c will be 
>> working
>> in the newest kernels, but not yet in most distro kernels.
>>
>> The -d flag is not permitted by libata, as the kernel prefers to 
>> completely
>> dictate DMA / PIO, and it does do a rather good job of it.
> 
> 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?

libata worries about speed changes for CRC errors and the like, not for 
media errors that involve sector relocation.

	Jeff




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