sudo mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1 --auto=md
mdadm: /dev/sda1 appears to contain an ext2fs file system
    size=312568640K  mtime=Wed Dec 31 19:00:00 1969
mdadm: /dev/sda1 appears to be part of a raid array:
    level=raid1 devices=2 ctime=Sun Mar 25 23:51:03 2007
mdadm: /dev/sdb1 appears to contain an ext2fs file system
    size=312568640K  mtime=Wed Dec 31 19:00:00 1969
mdadm: /dev/sdb1 appears to be part of a raid array:
    level=raid1 devices=2 ctime=Sun Mar 25 23:51:03 2007
Continue creating array?