Messages in this thread | | | Date | Tue, 22 Apr 2008 22:16:01 +0200 | From | "Francis Moreau" <> | Subject | Re: Disk geometry from /sys |
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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
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