[arch-general] Adding new disks > 2T to system that boots with grub, can GPT be used for new disks?

All, I'm confused by the partitioning wiki (https://wiki.archlinux.org/index.php/Partitioning). It says: If using GRUB legacy as the bootloader, one must use MBR What about adding disks to this system? Must they be partitioned MBR or can I use GPT on the additional disks. (I haven't used GPT before, so this has me stumped). Current setup is Arch booting from grub (grub2) on 1T raid1 mdadm array. I have a pair of 3T drives I want to add to the system. (as a 3T raid1 mdadm array). I want to use the entire disk in a single partition which is why I want to partition the disks GPT (leaving 100M unpartitioned at the end). Can I use GPT on the new disks, or am I stuck with MBR? -- David C. Rankin, J.D.,P.E.