Can't limit mdadm's detection

I've got a problem with mdadm and generating initrd.

I had some problems with one disk, so suddenly mdadm started detecting my raid1 arrays to be on hda, hdb2, hdb3 - even though they should really be on hda+hdb1, hda+hdb2, hda+hdb3. The system boots up from hdb3 without problems if I leave the mdadm to do raid autodetection (but each array uses only 1 drive of course). The problem starts when I want to disable the broken parts of the array to boot correctly and fix it. I created a file like this:

DEVICE /dev/hdb*
ARRAY /dev/md0 devices=/dev/hdb1 ...
ARRAY /dev/md1 devices=/dev/hdb2 ...
ARRAY /dev/md2 devices=/dev/hdb3 ...

but when I run update-initramfs -u, I get a message that the root is on /dev/md2 and it's not defined in my mdadm.conf. What could be wrong there? I can clearly see that the array is defined...

From serverfault viraptor

• mdadm --fail /to/faileddevice, mdadm --zero-superblock /to/faileddevice and then readd?

  From Ari