gmirror clearing configuration

> -----Original Message-----
> From: owner-freebsd-questionsfreebsd.org 
> [mailto:owner-freebsd-questionsfreebsd.org] On Behalf Of
Dave
> Sent: Friday, November 04, 2005 3:31 PM
> To: freebsd-questionsfreebsd.org
> Subject: gmirror clearing configuration
> 
> 
> Hello,
>     I'm trying to set up raid1 on fbsd 5.4-RELEASE no
patches 
> yet installed 
> just a vanilla release box. I've messed up somewhere,
the 
> primary drive is 
> smaller than the secondary drive and i'm using Ralf's
second 
> procedure. My 
> problem is i can't clear the metadata from either the
first 
> or second drive 
> so i can start again, i load gmirror then issue a
gmirror 
> clear and it says 
> it can't clear the metadata. Any help appreciated.
> Thanks.
> Dave.
>
I'm sure others have more gmirror experience than I do, but
maybe this
will help...

The metadata is stored in the last sector of the logical
disk.  Zap both
physical disks with 
  dd if=/dev/zero of=...  skip=n-1 count=1 bs=512b
where n is the number of sectors.  After you do this you'll
of course
need to rebuild the mirror.  Backup and be careful!!!

You can also do this with the gmirror utilities by removing
one drive
from the mirror, then undoing the mirror and the remaining
drive (which
zeroes the last sector) and then rebuilding.  When I tried
this once, I
had a little trouble with the fact that the removed drive
still had the
metadata on its last sector.  I think I had to zap its last
sector prior
to adding it back into the mirror.

-gayn

Bristol Systems Inc.
714/532-6776
www.bristolsystems.com 


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