結局これに落ち着くわけで。
/dev/sd[ab]をRAID1で
# mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sda /dev/sdb
途中経過はこんな感じ。
Every 2.0s: cat /proc/mdstat Sat Apr 5 01:09:02 2008
Personalities : [raid1]
md0 : active raid1 sdb[1] sda[0]
312571136 blocks [2/2] [UU]
[=>...................] resync = 6.8% (21260160/312571136) finish=60.1mi
n speed=80701K/sec
unused devices:
できた♪
Every 2.0s: cat /proc/mdstat Sat Apr 5 02:44:38 2008
Personalities : [raid1]
md0 : active raid1 sdb[1] sda[0]
312571136 blocks [2/2] [UU]
unused devices: