Comment 1 for bug 135391

Also worth mentioning (not explicitly mentioned above), it is a default configuration, including mdadm.conf:

root@FeistyFawn:~# cat /etc/mdadm/mdadm.conf
# mdadm.conf
#
# Please refer to mdadm.conf(5) for information about this file.
#

# by default, scan all partitions (/proc/partitions) for MD superblocks.
# alternatively, specify devices to scan, using wildcards if desired.
DEVICE partitions

# auto-create devices with Debian standard permissions
CREATE owner=root group=disk mode=0660 auto=yes

# automatically tag new arrays as belonging to the local system
HOMEHOST <system>

# instruct the monitoring daemon where to send mail alerts
MAILADDR root

# definitions of existing MD arrays

# This file was auto-generated on Tue, 07 Aug 2007 06:51:48 +1000
# by mkconf $Id: mkconf 261 2006-11-09 13:32:35Z madduck $