I tried adding a disk partition through Disk Utility on a Retina MBP under OS X 10.8.4. It was supposed to be a small, ~20 GB ExFAT partition on a 512 GB disk.
For some reason, my disk was partitioned into two equal partitions, with one being free space. When I try to remove the free space (either using regular Disk Utility or Disk Utility under recovery mode), the "–" to remove the disk is greyed out, and the "partition layout" dropdown is greyed out, as well. The numerical resize text box for the used partition is greyed out, but the one for the free space can be used, but the changes don't take effect. I tried erasing the disk, but I can only erase individual partitions, so I ended up erasing Macintosh HD (thankfully, I have a backup from before this issue started).
Finally I tried using
resizeVolume [volume name] limits to try and resize the volume manually, only to get
Error obtaining resizing information (is this a Mac OS 9 compatible "wrapped" HFS volume?)
How can I get rid of the ~256 GB block of free space on my disk, and expand the primary partition to occupy the entire disk, as it did originally?
EDIT: After playing around with
diskutil, I've found that the disk has a "bad partition map." How can this be fixed?