We believe that your issue has been closed by the upload of
Version 0.40 of grml-debootstrap from Michael Prokop <mika@grml.org>.
The explanation is attached below

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Hash: SHA1

Format: 1.8
Date: Mon, 18 Oct 2010 16:27:57 +0200
Source: grml-debootstrap
Binary: grml-debootstrap
Architecture: source all
Version: 0.40
Distribution: unstable
Urgency: low
Maintainer: Michael Prokop <mika@grml.org>
Changed-By: Michael Prokop <mika@grml.org>
Description: 
 grml-debootstrap - wrapper around debootstrap for installing plain Debian via grml
Changes: 
 grml-debootstrap (0.40) unstable; urgency=low
 .
   [ Christian Hofstaedtler ]
   * Create md raids with metadata format 0.90 when installing lenny, as
     grub from lenny can not boot from md with newer metadata versions.
     [Closes: issue878].
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* Christian Hofstaedtler wrote in grml's BTS on 20101011 / 13:35:

> Debian fixed this problem for *squeeze* in grub2 1.98+20100720-1 .
> Maybe special-case for RELEASE=lenny?

ACK, I think that's the way-to-go for us.

regards,
-mika-

Debian fixed this problem for *squeeze* in grub2 1.98+20100720-1 .
Maybe special-case for RELEASE=lenny?

JFTR: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=492897

With new grml 2010.04 mdadm creates a metadata layout which is incompatible with 
default debian lenny.

Raid 1 created with default settings can not be booted anymore with either grub 
or grub2 from lenny. It gives strange error messages on grub-install with 
something like "no mapping for device (md0) found".
This is not correctable without recreating the whole array.

mdadm --create needs an additional parameter -e0 to create metadata version 0.90.