mdadm problem creating device

["S Scharf" <ss11223@gmail.com>]

I installed a new disk and am trying to create a one disk raid 1 on it
(and will add the second disk later)

(Debian testing compiled with raid built into kernel)
$ cat /proc/mdstat 
Personalities : [linear] [raid1] [raid10] [multipath] [faulty] [raid6] [raid5] [raid4] 
unused devices: <none>

I have two partions on /dev/sda

$sudo fdisk -l /dev/sda

Disk /dev/sda: 400.0 GB, 400088457216 bytes
255 heads, 63 sectors/track, 48641 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x8b148706

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1          30      240943+  fd  Linux raid autodetect
/dev/sda2              31         517     3911827+  82  Linux swap / Solaris
/dev/sda3             518       48641   386556030   fd  Linux raid autodetect


but when I run mdadm I get the followng:

$ sudo mdadm --create /dev/md0 --level=raid1 --raid-devices=2 /dev/sda3 missing
mdadm: /dev/sda3 is too small: 0K
mdadm: create aborted

any help wil be appreciated.

Thanks
Stuart