non-partitionable array become partitionable after reboot

Binary package hint: mdadm

md0 + reboot = md_d0 :

Ubuntu 10.04 LTS
root@new357709:~# apt-cache policy mdadm
mdadm:
  Installed: 2.6.7.1-1ubuntu15
  Candidate: 2.6.7.1-1ubuntu15
  Version table:
 *** 2.6.7.1-1ubuntu15 0
        500 http://mirrors.service.softlayer.com/ubuntu/ lucid/main Packages
        100 /var/lib/dpkg/status

NOTE: array is degrated

root@new357709:~# mdadm --create /dev/md0 --auto=md -l mirror --raid-devices=2 /dev/sdb3 missing
mdadm: array /dev/md0 started.

root@new357709:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sdb3[0]
      479885568 blocks [2/1] [U_]

unused devices: <none>

root@new357709:~# reboot

root@new357709:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md_d0 : active raid1 sdb3[0]
      479885568 blocks [2/1] [U_]

unused devices: <none>