Onboard RAID and Ubuntu Install - Why Does it See Separate Disks?
Solution 1:
i've taken a look at mb specs. have you by any chance connected disk to ICH10R ports ?
what you describe sounds very much like there is soft-raid not a 'real raid' in use. those works fine with windows but do 'heavy lifting' [ xoring for raid5 ] on your main cpu instead of dedicated controller.
Solution 2:
Hate to say it.. but the Supermicro X8DT3-LN4F and all their new motherboards don't have Ubuntu support. The only drivers available are for RH or Suse.
On a side note... the onboard controller that comes with most motherboards is also called a 'fake raid' by some. There is more details on this provided in Ubuntu help area:
https://help.ubuntu.com/community/FakeRaidHowto
The end result was that I needed to drop the onboard raid and stick to native sata.
If I want RAID in the future I will need to buy a card.
Hope this helps