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

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Date:	Wed, 25 Feb 2009 15:49:58 -0800 (PST)
From:	david@...g.hm
To:	"Martin K. Petersen" <martin.petersen@...cle.com>
cc:	"H. Peter Anvin" <hpa@...or.com>, Matthew Wilcox <matthew@....cx>,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
	sandeen@...hat.com
Subject: Re: ATA support for 4k sector size

On Wed, 25 Feb 2009, Martin K. Petersen wrote:

>>>>>> "hpa" == H Peter Anvin <hpa@...or.com> writes:
>
>>> The two patches following this add support for drives which have
>>> sector sizes other than 512 bytes.  I haven't been able to test this
>>> as I don't have the hardware.
>
> hpa> What sector size do we report to user space for this?  I'm asking
> hpa> because logical sector size is visible in most partition formats.
>
> There are several flavors of drives we have to deal with:
>
> 512-byte logical / 512-byte hardware (current)
> 512-byte logical / 4096-byte hardware (ATA, doing read-modify-write)
> 4096-byte logical / 4096-byte hardware (SCSI initially, ATA later)

add to this good support for SSDs

?? logical / 128K hardware

or similar.

David Lang

> Because of 63-sector legacy problems a bunch of ATA vendors will
> initially ship 512/4096 drives that are not naturally aligned.
> I.e. logical sector 63 will be aligned on a 4KB hardware sector
> boundary to overcome the misaligned default partitioning.
>
> I have been working on some alignment patches the last week.  They hook
> into the stuff Matthew has been doing in libata and I'll post them
> shortly.
>
> For each block device you'll get a hardware sector size exposed as well
> as whether the device (partition) is naturally aligned or not.  This
> works for both ATA and SCSI devices.
>
> I'll defer to people like yourself for how this needs to work wrt. boot
> loaders and creating partition tables.  I'm CC:ing Eric Sandeen because
> he's also looking at this...
>
>
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