Re: Support for 4KB sectors size disk ?

[Thor Lancelot Simon <tls%panix.com@localhost>]

On Tue, Jan 12, 2010 at 03:55:26AM +0100, Johnny Billquist wrote:
>
> Well, technically any disk will have more than 512 bytes of data for  
> each sector. It's just that 512 bytes is what is presented to (and  
> usable by) the host system, and those disks by IBM are no different.
> They still present 512 byte sectors to the host OS. To quote the page  
> you linked to: "The data portion of the sector remains at 512-bytes for  
> all host systems."

No, they don't present 512 byte sectors to the host OS.  They present
512-byte sectors to *applcation code* running on the host -- this is
because the host OS uses the additional space itself.  The
sectors presented over the SCSI interface to the host are 524 bytes
or, in some older designs, 528 bytes.  Yank a disk out of a storage
array on one of these machines and see for yourself!

Most SCSI disks can be reformatted to almost arbitrary logical sector
sizes, to support this and other applications such as RAID arrays which
present a large sector size to the host so they can internally split
transactions more efficiently.