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How to fix an unmountable external USB drive on Mac?

Have a WD My Passport 4TB external drive. Ran First Aid first time. Message: macOS can’t repair the disk “disk-name”. You can still open or copy files on the disk, but you can't save changes to the files on the disk. Back up the disk and reformat it as soon as you can. At this point, I can see Location in Finder. First Aid continues running after this first message. After an hour... The First Aid process has failed. Problems were found with the partition map which might prevent booting the Whole disk required but a slice was passed. : (-69880) Operation failed... How can I back up? The drive doesn't show as a location in Finder at this point. The disk contains 600GB of files. How to proceed? Data recovery software?

Best Answered by

Anna Yuan

Answered on Monday, April 29, 2024

Since Disk Utility First Aid failed to repair your WD My Passport 4TB external drive, your external drive should be damaged severely and can't be mounted normally on Mac. As you can't see the drive in Mac Finder, you can't access the 600GB files in a normal way.

Luckily, you'll still have a chance to retrieve the 600GB files from the WD My Passport 4TB external drive with the help of professional data recovery software. That is iBoysoft Data Recovery for Mac. This powerful app is capable of recovering files from corrupted external hard drives, SSD, SD cards, and USB drives on Mac. 

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iBoysoft Data Recovery for Mac

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Downloading and launching this easy-to-use macOS program, use it to scan the corrupted/damaged WD external drive and search for any lost files, then you can preview the scanned results and recover all the files you want. 

After successfully recovering data from the WD external drive, you can format the external drive on Mac. Reconnecting the external drive again after reformatting, it should be mounted in the Mac Disk Utility and Mac Finder correctly.