Stuff

dephtu@dephtop:~$ sudo fdisk -l /dev/sda /dev/sdb

Disk /dev/sda: 320.0 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1       38913   312568641   83  Linux

Disk /dev/sdb: 320.0 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1       38913   312568641   83  Linux
dephtu@dephtop:~$ sudo modprobe raid1
dephtu@dephtop:~$ sudo mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1
mdadm: /dev/md0 does not appear to be an md device