Stephen C Woods wrote:

   Does the md driver support partitions in a meaningful/useful way?

No, the md driver (and many other block drivers in Linux) do not support 
partitions. Yes, you can use your tool of choice to put a partition 
table on the device, but it won't be used.

You can use LVM1/LVM2 to break up your md device into usable chunks 
(which is what I do).