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

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Message-ID: <4B9D8BB2.1010507@zytor.com>
Date:	Sun, 14 Mar 2010 18:21:54 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Denys Vlasenko <vda.linux@...glemail.com>
CC:	Arnd Bergmann <arnd@...db.de>, Tejun Heo <tj@...nel.org>,
	"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, jdelvare@...e.de
Subject: Re: ATA 4 KiB sector issues.

On 03/10/2010 01:14 AM, Denys Vlasenko wrote:
>
> 63s/255h is more or less "standard" now.
>
> Alignment issues can be solved by picking a good multiple of
> _heads_ or _cylinders_:
>
> For first partition, pick the start at 8th head:
>
> cyl 0 head 1 sector 1: LBA sector 63) - bad
> cyl 0 head 8 sector 1: LBA sector 8*63) - good (4k aligned)
>
> For any other partition, pick start cylinder which is a multiple of 8:
>
> cyl 8*x head 0 sector 1: LBA sector 8*x*255*63 - good (4k aligned)
>
> This will actually work well for *any* geometry, not only for 63s/255h.

Yes, but it does squat for a flash disk that wants, say, 256K alignment.

	-hpa
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