Hot answers tagged disk-utility
Have you tried looking at the kernel log messages? If, as you said earlier, it tried to root from the drive at least once, you can try to find it in the /var/log/system.log, for example: $ grep 'rooting\ via' /var/log/system.log Oct 24 18:01:44 localhost kernel: rooting via boot-uuid from /chosen: 4AB3D289-884F-379C-AF7B-************ Oct 25 11:21:57 ...
I had the same problem after converting a disk. There was a message displayed by diskutil cs convert: Couldn't unmount disk0s4; converted volume won't appear until it's unmounted I solved the problem by unmounting the disk and repairing it : diskutil unmount force disk0s4 diskutil repairVolume disk0s4
As has been touched on, this seems to be related to Mountain Lion setting itself up for encryption or a restore partition. I found that by selecting the partition table type in Disk Utility to MBR (yuck) instead of GPT or Apple's, this behavior is avoided and one gets the extra ~200MB usable space.
Only top voted, non community-wiki answers of a minimum length are eligible