grub on raid1 cannot mount filesystem

[Bruno Wolff III]

On Wed, Jun 29, 2011 at 23:16:01 +0200,
  Pavel Lisy <pali at tmapy.cz> wrote:
> 
> THIS DOESN'T WORK:
> grub> root (hd0,2)
> grub> setup (hd0,2)
> Error 17: cannot mount selected partition
> 
> Without mirror (raid1) it works. With raid1 it works only on first
> partition. Can you explain me why? 

One possible reason is that the raid information may be at the start of
the partition. You want to be using version 0.9 or 1.0. The default version
is 1.2. When installing anaconda gives the /boot partition the appropriate
version when creating the array. You can check the version with mdadm -D .