linux-kernel - Re: ATA support for 4k sector size

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Message-ID: <49BE7DEF.1060005@zytor.com>
Date:	Mon, 16 Mar 2009 09:27:27 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Greg Freemyer <greg.freemyer@...il.com>
CC:	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Matthew Wilcox <matthew@....cx>, Theodore Tso <tytso@....edu>,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
	sandeen@...hat.com
Subject: Re: ATA support for 4k sector size

Greg Freemyer wrote:
> If the reported geometry of these drives was changed to have sectors /
> track be a multiple of 8, wouldn't that fix most of the issues.
> 
> ie. If the drive were to report 56 sectors per track, then a
> traditional partitioning tool would start the first partition as
> sector 56 and a Vista like partitioning tool would place the first
> partition at sector 2048.  Both would have the same 4K sector
> alignment.
> 
> If my logic is sound, anyway to get this recommendation upstream to
> hardware manufacturers.  It seems like an almost trivial change for
> them.
> 
> FYI: It sounds to me like partitioning tools should totally drop
> efforts to align with cylinders, instead they should start asking what
> the unit of atomic read/writes is at the physical layer and if any
> offsets are needed to align the partition with the atomic write areas.
> 
> That would fit better for both SSD technology and for this 4K sectors
> issue than trying to continue to support cylinders at all.

As long as BIOSes played along with it (which some of them may not do --
remember the geometry that matters is the one reported by the BIOS)
However, it definitely would be a major step in the right direction, as
it would let *most* systems Do The Right Thing instead of weirdly
misaligning the partitions and trying to cope with that.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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