Recently my one and only external drive developed a problem having become 'read only'. This drive holds my Aperture Library and my Time Machine backups. I can't even mount the disk, to be able to use Carbon Copy Cloner with a new external drive. The Disk Utility message at the base of my post……I can't back up any of my files if I can't mount the disk….can I? Seem to be going round in ever decreasing vicious circles. So before I have to go to Data Recovery, what else could I possibly try? OS 10.8.5. I don't really want to have to install a later OS because then Aperture won't work and is not longer available at the App Store. I will bring forward my plan of migrating everything to LR, but perhaps I have left it too late……story of my life! Error: Disk Utility can’t repair this disk. Back up as many of your files as possible, reformat the disk, and restore your backed-up files.