linux-kernel - Re: tools support for non-512 byte sector sizes

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Date:	Wed, 30 Jul 2008 14:28:12 -0400
From:	Ric Wheeler <rwheeler@...hat.com>
To:	Theodore Tso <tytso@....edu>, Matt Domsch <Matt_Domsch@...l.com>,
	Jim Meyering <jim@...ering.net>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Matthew Wilcox <matthew@....cx>,
	Ric Wheeler <rwheeler@...hat.com>, linux-scsi@...r.kernel.org,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jeff Garzik <jeff@...zik.org>
Subject: Re: tools support for non-512 byte sector sizes

Theodore Tso wrote:
> On Wed, Jul 30, 2008 at 12:29:22PM -0500, Matt Domsch wrote:
>   
>> 2) those that report a 512-byte sector size, but are really a
>>    4096-byte size, and the drive does the conversions and
>>    read/modify/write.  T10 and T13 are looking to add commands to
>>    expose this different underlying physical sector size so the OS
>>    could be aware of it.  This is primarily being driven to mitigate
>>    any problems that may happen with "legacy" OSs that are not aware
>>    of the difference.
>>     
>
> As usual, the biggest problem will be "legacy" userspace.  For
> example, most partition tools are still generating legacy partition
> tables that look like this:
>
> Disk /dev/sda: 255 heads, 63 sectors, 38913 cylinders
>
> Nr AF  Hd Sec  Cyl  Hd Sec  Cyl     Start      Size ID
>  1 80   1   1    0 254  63  121         63    1959867 83
>  2 00   0   1  122 254  63  619    1959930    8000370 82
>  3 00   0   1  620 254  63 1023    9960300  615177045 05
>  4 00   0   0    0   0   0    0          0          0 00
>  5 00   1   1  620 254  63 1023         63  615176982 8e
>
> Note the starting sector# for the first partition.....
>
> 						- Ted
>   
If I remember correctly, the MS Vista new alignment for data partitions 
is on a 0 offset, 1MB aligned boundary. The support for 4096 byte 
sectors is only for data partitions (not boot).

Array vendors, who consume a fair amount of drives, are most likely more 
friendly to native 4k drives. The big fear from disk vendors is getting 
a wave of returns from Best Buy, etc when people go and plug in a new, 
native 4k drive into an old box....

ric

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