Backup disc can't be repaired

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Level 1

19 points

Backup disc can't be repaired

I'm running OS 10.15.7 Catalina on a 2013 27" iMac and back up using Time Machine to a WD My Passport for Mac.

The backup disc now fails to appear on the desktop. Disk Utility ran even though the disc was unmounted, but failed to repair it. It mentions an invalid parent for some directories and incorrect number of directory hard links, and states that it could not be verified completely. Then:

File system check exit code is 8.

Restoring the original state found as unmounted.

File system verify or repair failed. : (-69845).

Operation failed…

I got First Aid to run again, with the same result.

I would be happy to delete everything on the backup disc if necessary and just reformat it and back up again from the iMac, but the "restore" option is blanked out and doesn't go ahead. I'm not even sure whether I should be working on the container disc in the sidebar or the item labelled "backup disc". And I'm sorry but anything I try to read about this just confuses me with more and more options I don't understand!

iMac 27″, macOS 10.15

Posted on Jul 23, 2025 07:43 PM

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Answer 1

Top-ranking reply

Matti Haveri

Level 6

19,104 points

Jul 24, 2025 12:15 AM in response to tupppi

In Disk Utility > View > Show All Devices and select the topmost device (not volumes under it) and erase it as APFS (GUID). If that fails, it indicates that the disk is bad and must be replaced. As a last option could try to erase the disk as FAT (Master Boot Record) and after that as APFS or MacOS Extended (GUID) to try to reset the partition table.

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Answer 2

Jeff

Level 6

12,316 points

Jul 24, 2025 01:30 AM in response to tupppi

What you have described is directory corruption. For years, Alsoft's DiskWarrior has provided the best solution for Mac users to correct that problem. It creates a new directory, rather than repairing a damaged one. Its capabilities have always exceeded those of the old "Disk First Aid" and later, "Disk Utility." Reformatting the backup drive is likely unnecessary, so I suggest that you check it out.

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Answer 3

tupppi Author

Level 1

19 points

Jul 24, 2025 08:17 AM in response to Matti Haveri

Thanks so much, Matti. Success!

I erased the disc as APFS (GUID) and it created a container volume, but Time Machine wanted to erase the volume again because it said it "has an incompatible file system". Idk. But the container disappeared and TM started backing up.

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