2 copies of Macintosh HD - Data seen by TimeMachine

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2 copies of Macintosh HD - Data seen by TimeMachine

3 weeks ago I upgraded to Big Sur. Everything was fine until I tried to back up using Time Machine today, when I received an error message saying it could not back up because there were 2 disks with the same name, and I should rename one of the disks named Macintosh HD - Data.

I opened Disk Utility, renamed one of the Macintosh HD - Data disks, dismounted my backup drive, remounted it and tried again. No improvement. I restarted my Mac. No improvement. I've repeated this several times, each time without any success.

From a number of blog posts I've read this appears to be a problem with Time Machine under Catalina and Big Sur. Is there any solution, or should I just give up because Time Machine is a lost cause?

Thanks for any help you may be able to give.

Posted on Aug 17, 2021 12:01 AM

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Answer 1

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Barney-15E

Level 10

113,034 points

Aug 17, 2021 4:45 AM in response to Limeyinkl

The problem is the orphaned - Data volumes.

Unless you have multiple boot drives, you should never see the Data volumes in Finder.

When you list the volumes in Disk Utility, select each Data volume. The one with the home icon on it is the current one and the other(s) orphaned. You can also look at the Mount Point. The orphans will be mounted to /Volumes.

You can remove the orphans by selecting it in Disk Utility and clicking the Remove Volume button (–). I have yet to see it not transfer all of the data, but you might want to make sure all of your files are inside your home folder before removing the orphan.

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Answer 2

Limeyinkl Author

Level 1

8 points

Aug 17, 2021 8:32 PM in response to Barney-15E

Many thanks indeed, Barney - that's a great help. I'll follow your suggestions and hopefully I can get Time Machine back up and running quickly. I figured the volume without the house icon was the defunct one as it has very little in it (just 3.2 GB), but wasn't sure until I read your post above.

Here's some history for the record, and for anyone who's having similar issues and is reading this. Before my problems with Time Machine, I upgraded my MacBook Pro to Big Sur directly from Mohave. It took three attempts. The first attempt failed - I received an error message and the installation stopped. I don't know what the reason was. The second attempt worked, but I received an error message at each startup warning me of an incompatible volume. After a bit of head-scratching, I discovered I had selected the wrong volume to install the OS onto. Looking back, I think I'd chosen "Macintosh HD - Data" when it should have been "Macintosh HD". Realizing my mistake, I re-installed Big Sur onto the correct volume and then everything worked fine, until the issue with Time Machine occurred yesterday. I guess my final installation did not remove that first incarnation of the "Macintosh HD - Data" volume, thereby causing the problem you describe.

I really want to avoid replacing Time Machine with a third-party app, because it's such a handy utility. I've gone for about 10 days without a backup, so I'll manually save my Outlook messages to an external drive before I remove the defunct volume. All my documents, photos and music are in iCloud, so should be safe.

Once again, many thanks for your help.

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Answer 3

Limeyinkl Author

Level 1

8 points

Aug 19, 2021 3:13 AM in response to Barney-15E

Quick update - I followed your instructions and Time Machine is now working properly. I had to reboot my MacBook and open and close System Preferences - Time Machine twice to clear the error, but all is now good. Many thanks again.

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2 copies of Macintosh HD - Data seen by TimeMachine

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