Re: [PATCH] pdcraid and weird IDE geometry

From: Andries Brouwer (
Date: Thu Jul 17 2003 - 11:03:28 EST

On Thu, Jul 17, 2003 at 11:34:11AM -0400, Jeff Garzik wrote:

> Can't you fix the geometry from fdisk expert mode?
> I've done that several times before, when otherwise like-sized disks
> appeared with vastly different geometry.

It is easiest to think that it is meaningless what you say
(in this case). A disk does not have a geometry, and
moreover you cannot change it with fdisk.

However, under some circumstances, some kernels will guess
a (translated) geometry from a DOS-type partition table,
so it is true that under some kernel versions you can use
fdisk to change the kernel's ideas about disk geometry.
A very fragile activity.

[Moreover, there are several kinds of geometry, and the present
authors of ide-disk.c conveniently confused them all.
Concerning pdcraid, I don't know for which of the possible
ideas of geometry it is true that one needs the first sector
of the last cylinder.]


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