Comment 1 for bug 1284196

Upon further investigation, it seems to be the placement of the grub.cfg file, not of the kernel, that's causing GRUB to flake out. Using debugfs, I found that grub.cfg resides at blocks 748716118 and 748716119. Given a 4KiB block size, that works out to about the 2.79TiB mark on the disk, which is presumably above a GRUB or BIOS 2^32 sector limit. Attempting to do an "ls (hd0,gpt2)/boot/grub" from the "grub rescue>" prompt results in the same "attempt to read or write outside disk" error message noted earlier.

This therefore looks like a GRUB and/or BIOS limitation; however, because larger disks are becoming increasingly common, I believe it's prudent to work around this bug in Ubiquity, at least unless and until a workaround or fix can be added to GRUB.