linux-kernel - Re: ATA 4 KiB sector issues.

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Date:	Tue, 16 Mar 2010 15:21:51 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ric Wheeler <rwheeler@...hat.com>, Tejun Heo <tj@...nel.org>
CC:	James Bottomley <James.Bottomley@...e.de>,
	Denys Vlasenko <vda.linux@...glemail.com>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Daniel Taylor <Daniel.Taylor@....com>,
	Jeff Garzik <jeff@...zik.org>, Mark Lord <kernel@...savvy.com>,
	tytso@....edu, hirofumi@...l.parknet.co.jp,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, irtiger@...il.com,
	Matthew Wilcox <matthew@....cx>, aschnell@...e.de,
	knikanth@...e.de
Subject: Re: ATA 4 KiB sector issues.

The only reason I see to care about CHS at all is that there are systems in the field which can only boot from USB in CHS mode, and which often look at the MBR partition table to guess the geometry.  Of course, some then *report* the detected geometry but don't *use* the detected geometry...

"Ric Wheeler" <rwheeler@...hat.com> wrote:

>On 03/16/2010 11:37 AM, Tejun Heo wrote:
>> Hello,
>>
>> On 03/17/2010 12:23 AM, James Bottomley wrote:
>>    
>>>> So, using custom geometry doesn't help compatibility at all.
>>>>        
>>> Our partitioning tool still obey the integral cylinder rule ... we can
>>> argue about whether they should, but what we need is a strategy for
>>> fixing what is rather than what should be.
>>>      
>> The updated ones don't anymore.  They just align to 1MiB + whatever
>> the drive requests for offset (the offset-by-one thing).  They will
>> basically behave the same as windows vista/7 ones, so it's already
>> fixed.  What we can argue is whether adding CHS tricks on top to make
>> those larger alignments somewhat meaningful w/ CHS interpretation too,
>> which I'm objecting on the ground that it doesn't help compatibility
>> at all.
>>
>> Thanks.
>>
>>    
>
>Dropping any mention of CHS seems to be the only sensible thing. Why 
>waste any time to continue some myth about drives that no modern 
>hardware supports (and then have the joy of explaining that to users)?
>
>Talking about it only confuses people and in the worst case, could cause 
>them to misalign their partitions by clinging to these pretend borders :-)
>
>ric
>

--
Sent from my mobile phone, pardon any lack of formatting.