I have an external HD I use for storage of things that won't fit on my MacBook Pro (late 2012). Today, seemingly out of the blue, I booted up my computer and it said that the external disk couldn't be repaired, and I need to format it. I tried to repair it in Disk Utility and it gave me the error message "incorrect number of thread records." It tried and failed to repair three times. So I have two questions, First, are there any further options I can try to repair this disk without reformatting? Second, if I do have to reformat, is there any way I can try to pull off whatever data I can? I have most of the stuff on this drive backed up, but I haven't been able to back up in about three weeks as I've been travelling. So it'd be nice to not lose the things I've added since.