Re: Disk geometry from /sys

["Francis Moreau" <francis.moro@gmail.com>]

Hello Mark

On Fri, Apr 18, 2008 at 3:22 PM, Mark Lord <lkml@rtr.ca> wrote:
>  That can sound a bit misleading.  The complete story, for ATA/SATA drives,
>  is that the disk has two geometries:  an internal physical one, with a
> fixed number of heads and cylinders, but variable sectors/track
>  (which normally varies by cylinder zone).
>
>  Software *never* sees or knows about that geometry, so ignore it.
>
>  The second geometry, is the one that the drive reports to software
>  as its "native" geometry.  This is what you see from "hdparm -I"
>  and friends, and this geometry is what has to be used by software
>  when using cylinder/head/sector (CHS) addressing for I/O operations.
>  The hardware interface has a limit of 4-bits for the head value,
>  so the maximum number of heads can never be more than 16.
>
>  Nobody uses CHS addressing for I/O operations, at least not on
>  any hardware newer than at least ten years old, so this geometry
>  is also unimportant for most uses.
>

Is it because IDE drives support several IO operation modes ?

thanks
-- 
Francis