Thank you for your helpful comment. I did not experiment with this myself.
Yes, LILO lacks support for GPT tables. This does not prevent its use on boot devices of exactly 2 TB with MBR partition tables, though (we currently have many Owl installs with LILO on 2 TB devices, although we obviously tend to allocate just a small partition for the boot/root filesystem). My current understanding is that things should continue to work with MBR partitions for boot device size of up to 4 TB, but with individual partitions no larger than 2 TB each. (I have not tested this, though.) With larger RAID arrays (and eventually larger individual disks as well), the current workaround (while staying with LILO) would be to allocate a smaller device for booting from (e.g., put the first two disks into a RAID-1 array, put the rest into a RAID array bigger than 2 TB or 4 TB). Yes, this is a nasty limitation and a reason for us to move to a bootloader that is still being enhanced (or at least has been recently) rather than is merely maintained (like LILO mostly is, with occasional changes to its existing functionality but no new functionality being added).