RAID setup using mdadm on VMs in VMWare Server

Hi,

I have the following 64 bit installation of vmware server, which has a 64 bit Gentoo 2006 guest installed on it.

I have 4 scsi virtual disks added to the VM, showing up as sda, sdb, sdc, sdd.

I am using 'mdadm' to set up a RAID across the paritions sdx1.  Steps to this include

\*  mknod /dev/md0 b 9 0

\*  mdadm --create  /dev/md0 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1

FAILS with

>>> mdadm: error opening /dev/md0: No such device or address

Digging up mdadm code, all it is trying to do is to open("/dev/md0", O_RDWR, 0)

which fails with  errno = ENXIO            6      /* No such device or address */

I am obviously missing something fundamental related to creating such devices in a VM.  Can somebody throw some light ?

Thanks,