I had a 6TB Hardware RAID volume that I couldn't boot from (in RHEL5).
What I did was the following:
In my hardware RAID controller I carved off a 1GB volume. That 1GB volume appears to the BIOS and Linux as /dev/sda. The other 5999GB volume shows up as /dev/sdb. Both volumes come from the same RAID6 volume set.
My /dev/sda has one fdisk MBR style partition that uses the whole device, -- it holds /boot. I boot off of it.
My 5999GB volume has a GPT partition table, uses LVM (maybe I could have skipped the GPT partition table altogether), and has Linux installed to it.