Using DISKPART - Missing HD Space?

Hello.  I've setup a new Hyper-V 2012 R2 server on a new HP RAID-6 box with a single 4TB logical disk (to keep it simple).  However, I'm unable to realize all 4TB as shown by DISKPART (as I'm in the thin "shell" layer, so the VMs and such should be a moot point in all this).  Output as follows:

DISKPART> select disk 0

Disk 0 is now the selected disk.

DISKPART> list disk

  Disk ###  Status         Size     Free     Dyn  Gpt
  --------  -------------  -------  -------  ---  ---
* Disk 0    Online         4471 GB      0 B

DISKPART> list partition

  Partition ###  Type              Size     Offset
  -------------  ----------------  -------  -------
  Partition 1    Primary            350 MB  1024 KB
  Partition 2    Primary            287 GB   351 MB
  Partition 3    Primary           1760 GB   288 GB

DISKPART> create partition primary

Virtual Disk Service error:
There is not enough usable space for this operation.

Any idea why  I can't the setup the rest of the 2.xTB of space from the original 4TB for my purposes?  As it stands, I have unallocated space which I dearly need.

Thanks all.