A bit stuck on this one. We've two macs, one running 10.10, the other (now) running 10.7. I have backed up for years with no problems to a WD external 500GB USB 2 disk, however this has become full. I've therefore bought an Akasa USB3 enclose and WD Green 3Gb - when I format this as per Time Machine instructions, it will back up both computers once or twice, then will hang midway through an incremental backup on one of them. I then get an error saying the backup cannot be completed; running Disk Utility gets File System Check Exit Code 8, and a statement that the disk cannot be repaired - as this has happened three or four times, followed by me having to reformat, it's all getting a bit tiresome. fsck cannot verify the volume completely. Anyone have any suggestions?