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

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Message-ID: <yq1fx4aa7nq.fsf@sermon.lab.mkp.net>
Date:	Mon, 08 Mar 2010 15:19:05 -0500
From:	"Martin K. Petersen" <martin.petersen@...cle.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	"Martin K. Petersen" <martin.petersen@...cle.com>,
	James Bottomley <James.Bottomley@...e.de>,
	Tejun Heo <tj@...nel.org>,
	"linux-ide\@vger.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.

>>>>> "hpa" == H Peter Anvin <hpa@...or.com> writes:

hpa> On the flipside, though, there really is very little net benefit to
hpa> 4K as opposed to 512 byte logical sectors: the additional protocol
hpa> overhead is relatively minimal, and as long as writes are aligned
hpa> full blocks, there shouldn't be any additional overhead on either
hpa> the OS or the drive side.  On the plus side, you get full
hpa> compatibility with the existing software stack.  The equation
hpa> really seems rather simple.

4KB sectors are not a win for anybody except the drive vendors.

There is a push in the industry right now to keep the 512-byte logical
blocks forever.  The first step would be to report misaligned accesses
or accesses that are not a multiple of the physical block size.  Second
step would be to eventually reject any write that's not a properly
aligned multiple of the physical block size.

-- 
Martin K. Petersen	Oracle Linux Engineering
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