I got a USB 3.0 Passport for Mac (500GB) for my folks to backup to using Time Machine. It backed up regularly for about 2 months with no issue. Then one day Time Machine fails to make a backup. I couldn't read or see the drive in Finder, so I used Disk Utility to Verify Disk and Repair Disk as necessary. I had to boot into the Recovery HD in order to run it successfully though. Once I did, Time Machine was able to read and backup the drive again. Until the next day, when it fails once again, and I have to start the process of verifying/repairing the disk. It's been doing this crap 3 days in a row now. I would have figured that if the drive was truly defective I wouldn't have been able to to repair the disk and get Time Machine to backup to it again at all. Are there other solutions I can try? My next step is to re-format the disk and start from scratch again, only this time remove the partition WD reserve for its proprietary software and really wipe this drive clean, but it feels like I may be missing something obvious here. Assuming the drive is in fact not defective.