Can't format external hard drive, damaged partition map... (-69879 error)

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Can't format external hard drive, damaged partition map... (-69879 error)

Hi,

The issue I have is that I cannot format my external USB hard drive. Here's what happened...

I've used this external hard disk as a Time Machine drive for years. Now, I've just bought a TP-Link Archer AX55 (AX3000) router, which supports Time Machine over Wi-Fi. As there wasn't much in terms of instructions, I simply plugged my hard drive in the router's USB port. I could get the backup to start, so it seemed to work, but, at some point, I ran out of space disk, which by the way never happens when I plug the device directly to my Mac, as Time Machine automatically deletes older files to make space as needed, but anyway... I tried to plug the drive again directly into my Mac, but the disk doesn't mount anymore. It seems like the partition map was changed by the router, and it's no longer readable from my Mac. At this point and after trying several fixes, I was willing to format the disk and start from scratch, but I can't even do that anymore; Disk Utility won't work, even in recovery mode, and I've tried just about every type of format... I get an error, "-69879: Couldn't open disk".

All I want now is to wipe the disk and start anew... I also have access to Windows through BootCamp, but that hasn't helped so far... The crazy thing is that if I plug my hard drive on my router again, I can browse the files remotely, from my Mac, so it's not like the drive is physically broken or anything...

Any ideas on how I could go about fixing the issue, that is simply manage to format the disk and start afresh?

Thank you very much!

Etienne

MacBook Pro 13″, macOS 10.15

Posted on Jan 6, 2023 4:53 PM

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Answer 1

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HWTech

Level 9

68,756 points

Jan 7, 2023 8:11 PM in response to etiennelj

I don't use TM, but I have seen some more knowledgeable contributors mention (at least with macOS 11.x+) that sometimes you must launch the TM app and disassociate that backup drive from TM before Disk Utility will erase the backup drive...probably a safety feature to protect the backup drive from accidental erasure.

If that doesn't work, then try connecting the drive to a non-Apple PC and partition & format the drive there, then connect it to the Mac to use Disk Utility to erase the drive again for use on macOS. If you are familiar with the command line, then there is a way to attempt to destroy the partition table on the external drive, but it is tricky to explain and risky since the command line has no safety nets like the macOS GUI so a mistake could destroy data accidentally and may not even work here since this was a TM drive which macOS may be protecting.

FYI, I personally would not connect a drive to the USB port of a router (for any reason) since router's don't have the best track record. Even more so for a backup drive. Even users utilizing a NAS solution which supports networked TM backps, sometimes issues can still occur from time to time. Even if the router officially supports TM backups with the router's USB port, I personally would not trust it. The most reliable TM backups will be when the TM backup drive is connected directly to the Mac...the only other option would be to backup to a NAS device which officially supports TM backups.

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Answer 2

etiennelj Author

Level 1

4 points

Jan 7, 2023 8:52 PM in response to HWTech

Thank you for your kind reply!

What I've just managed to do is to format the drive using Windows' command prompt (https://www.tomshardware.com/news/format-hard-drive-command-prompt,37632.html). That's the only thing that worked...

And I think I'll follow your advice and stick with using TM with my hard drive connected directly to my Mac...

Thanks again!

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Can't format external hard drive, damaged partition map... (-69879 error)

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