"OS X can't repair the disk Time Machine". However, I can still access files directly from the TM disk, and even (haltingly) via the TM app. So I hate to reformat the disk, since the data might be useful. But it's a big 1TB drive....an awful lot to back up elsewhere. What do I do? Just buy a new TM drive and keep this on hand for a year or two in case I need to go to it for data?