OK, some weirdness is happening. I cloned my Mac Pro boot drive onto a G-Raid Mini. Then I cloned it onto Macbook Pro's internal drive. If I boot the Mac Pro with the clone on the G-Raid Mini it works flawlessly. If I boot the Macbook Pro from the clone on the internal drive it works flawlessly. However...If I try and boot the Macbook Pro from the clone on the G-Raid Mini it just doesn't work. BUt it's exactly the same as the clone that is installed AND working on the internal drive. AND this very same drive will boot the Mac Pro perfectly well. If I hold down the option key at boot it just won't see the clone on the G-Raid Mini, it's not listed in the drives. BUT if I go into system prefs it shows up in Start-up Disk but then if I try to restart from it it just reverts back to the internal drive. I've tried a few different options with partitions, no partitions. repairing, re cloning again and again, Not had any luck though. Strangely enough I have another clone on a USB2 disk which boots fine on the same Macbook Pro. It tends to suggest it's something to do with the disk but the disk boots the Mac Pro perfectly well. I want to use the G Raid Mini as a backup boot disk for location work. It leaves me very confused. Any ideas?