Currently booting from a 750G BIOS-partitioned disk.
Trying to enable booting from the 4.7T drive, which is GPT partitioned.

With grub-install I get errors:

april:/farhome/hendrik# grub-install /dev/sda
Installing for i386-pc platform.
grub-install: warning: this GPT partition label contains no BIOS Boot Partition; embedding won't be possible.
grub-install: error: embedding is not possible, but this is required for RAID and LVM install.
april:/farhome/hendrik#

Evidently there is some kind of incompatibility here.

What is going on? What can I to do other than continuing to boot from
small BIOS disks?

-- hendrik