Has Software Mirror stuff in SLES 11 / OES11 changed

Tried deleting partion using - Linux, DRDos, MSDOS, Windows XP

But SLES11 is screwing things up - (or it could be me ! screwing things up)
it even messes up the SOURCE disk

If I clone a OES11 installion using the mirror updates in SECONDS

watch cat /proc/mdstat <--- open a terminal window and monitor progress

sfdisk -d /dev/sda | sfdisk /dev/sdb <-- Clone Disk Partitions

mdadm /dev/md0 --add /dev/sdb2 <--- add disk partition to mirror
mdadm /dev/md1 --add /dev/sdb3 <--- add disk partition to mirror

This Procedures work fine if the DISK is NEW - straight out of the box
(unused)
But If I take a disk from the RAID and REUSE it after Fdisk / dos / linux
etc

and... the above works FINE on NOWS SBE - which is SLES 10 (also OES2 which
is the same)
I've done this around a hundred times ! to for Testing various installtions.

So I guess I need some sort of disk clearing utility or more FACTORY
formatted disks !
OES 11 always messes up even after deleting partions - I tried deleting
partion using - Linux, DRDos, MSDOS, Windows XP