Adding a new mirror disk to RAID1 configuration

I have a system with two 40GB drives, and the first drive (hda) is setup 
  under an md device with RAID1 driving it.  I'm trying to now make the 
second disk, hdc, a mirror of the first.  When I try to add it using 
mdadm the second disk becomes a spare and no synchronization is done. 
Is there any way to add the second disk directly as a mirror?  Thanks.

	Luke Reeves
	http://www.neuro-tech.net/