WD20EARS will not partition as primary in Ubuntu

I am trying to set up a large scale server using WD20EARS, WD15EARS and WD15EADS drives.  The 2tb drives do not allow me to select Primary or Logical when creatign partitions and I cannot select Bootable Flag=On if I use them as Physical Volume for Raid.  Thus the GRUB loader fails to install.

Question: why would the 2TB version not give me the option or designation of Primary or Logical partion (it displays nothing), wheras the 1.5TB drives give me the choice and display the chosen state.

Please keep your responses at the novice level.

i think is the limitation is the BIOSof the MB