FC3 mdadm issue

I created md0-3 during boot and now want to create another raid device which would be md4.  I've gone through the man page and searched online but am coming up blanks for an answer.  I am using FC3 x86_64...

To create the new raid device I ran:  mdadm --create /dev/md4 --level=0 --raid-disks=2 /dev/hda6 /dev/hdc6 which errors out stating: mdadm: error opening /dev/md4: No such file or directory.  Of course it's not there yet, I'm just now trying to create it.

The partitions are ready:

fdisk -l

Disk /dev/hda: 120.0 GB, 120034123776 bytes
255 heads, 63 sectors/track, 14593 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/hda1   *           1          13      104391   fd  Linux raid autodetect
/dev/hda2              14        1288    10241437+  fd  Linux raid autodetect
/dev/hda3            1289        1543     2048287+  fd  Linux raid autodetect
/dev/hda4            1544       14593   104824125    5  Extended
/dev/hda5            1544        1674     1052226   fd  Linux raid autodetect
/dev/hda6            1675       14593   103771836   fd  Linux raid autodetect

Disk /dev/hdc: 120.0 GB, 120034123776 bytes
255 heads, 63 sectors/track, 14593 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/hdc1   *           1          13      104391   fd  Linux raid autodetect
/dev/hdc2              14        1288    10241437+  fd  Linux raid autodetect
/dev/hdc3            1289        1543     2048287+  fd  Linux raid autodetect
/dev/hdc4            1544       14593   104824125    5  Extended
/dev/hdc5            1544        1674     1052226   fd  Linux raid autodetect
/dev/hdc6            1675       14593   103771836   fd  Linux raid autodetect

So, the question is why am I unable to create /dev/md4?  Has anyone else ran across this?  Ideas/suggestions?

TIA!

Aaron