clear metadata using dd?

[Gary Palmer]

On Mon, Jan 08, 2007 at 07:45:06PM -0300, Fernan Aguero wrote:
> Hi
> 
> I'm trying to set up two disks to contain both gmirrored and gstriped 
> slices.
> 
> This is what I'm trying to achieve:
> adxs1, swap
> adxs2, gmirror
> adxs3, gstripe
> 
> I already got the first and second slices set up (swap and gmirror 
> containing
> the active, root partition), but I cannot seem to be able to set up s3 into 
> a
> gstripped device.
> 
> gama# gstripe label -v gs0 /dev/ad4s3 /dev/ad6s3
> Can't store metadata on /dev/ad4s3: Operation not permitted.
> 
> This might be because ad4s3 had been part of a gmirror device before I
> reorganized my disks and moved the mirror to the s2 slice.
> 
> Gayn Winters suggested that:
> "The geom metadata is stored in the last block of the slice.  Zero it as
> well and you can have a clean start."
> http://lists.freebsd.org/pipermail/freebsd-questions/2006-May/120950.html
> 
> But now I wonder what is the magic incantation to run dd for targeting the 
> last
> (sector?) of ad4s3?

Any reason that "gstripe clear" or "gmirror clear" doesn't work?  Thats what
they're meant to do, as far as I know.