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Macintosh HD - Data - Data

When I went to install the Big Sur update, it asked me a question about which drive to install it on. I told it Macintosh HD. When the installer rebooted it got caught in a reboot loop. Fortunately I had a time machine backup that i was able to restore from once I reinstalled MacOS Catalina.


I didn't realize at the time that the latest version of MacOS Catalina had actually been installed on Macintosh HD - Data and that my data was being stored on Macintosh HD - Data - Data.


When i look at the disk in Disk Utility and confirm what disk i was actually booted from using the Startup Disk utility what I see is Macintosh HD (macOS 10.15.1) , Macintosh HD - Data (macOS 10.15.7), and Macintosh Data - Data.


I'm reluctant to try the Big Sur install again in this configuration although I expect it would work correctly if I chose to install it to Macintosh HD - Data this time.


Is there a way to straighten this out short of reloading macOS from scratch and restoring the time machine backup again?

MacBook Pro with Touch Bar

Posted on Nov 18, 2020 9:33 AM

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8 replies

Nov 23, 2020 7:02 AM in response to Kenneth Cohen1

Kenneth Cohen1 wrote:

Hi. I have two data "volumes" as well. To me this is a bug as the only solution is to erase my entire internal drive, then reinstall everything from a backup, something many users will have to deal with without knowing what to do next. My question is, can I copy all the data from the second Macintosh - data to the first, and then delete the second data "volume?"

Alternatively, what if I just leave the two data volumes in place. Is there any reason not to do this?

Thanks for your help (and letting me vent a little).

Ken Cohen



All volumes 'share' space under their same Container. You can simply delete the extra (un-needed Volumes using the +/- option.


You can see the whole enchilada ref:

https://discussions.apple.com/thread/252028399?answerId=253858967022#253858967022


(note: Big Sur System always boots from a snapshot, this is normal for macOS 11.0.1 )


Add, delete, or erase APFS volumes in Disk Utility on Mac ...

https://support.apple.com/guide/disk-utility/add-erase-or-delete-apfs-volumes-dskua9e6a110/mac


Nov 23, 2020 8:44 AM in response to Kenneth Cohen1

Kenneth Cohen1 wrote:

Hi. I have two data "volumes" as well. To me this is a bug as the only solution is to erase my entire internal drive, then reinstall everything from a backup, something many users will have to deal with without knowing what to do next.

This usually happens when a user selects the incorrect volume when reinstalling Catalina or installing Big Sur. Normally when presented with multiple volumes for reinstalling Catalina or upgrading to Big Sur you should choose the "Macintosh HD" volume and not a " - Data" volume. Unfortunately Apple has removed/changed the article which properly showed how to reinstall Catalina over top of itself including which volume to select as the destination.


My question is, can I copy all the data from the second Macintosh - data to the first, and then delete the second data "volume?"

Most likely you are using the second "Macintosh HD - Data - Data" volume for your user account and the "Macintosh HD - Data" volume as your read-only macOS system drive. If you can confirm which volumes are currently being used, then you can move your files over to the current volume (whatever it may be). Delete the volume that is not being used. Then use Disk Utility to rename the read-only system volume as "Macintosh HD" which should also properly rename the read+write volume containing your user folder and data.


Alternatively, what if I just leave the two data volumes in place. Is there any reason not to do this?

It will just take up space and potentially cause confusion later on especially if you go to upgrade or reinstall macOS again.


As long as you have a good backup, then you can attempt to remove the unneeded volume. Of course completely erasing the whole physical drive and restoring from a backup made before the change may be the easiest way to fix things. It is a shame that Apple didn't provide enough information during the OS install/upgrade to educate the user.

Nov 18, 2020 6:09 PM in response to JeffHouTX

While you may be able to delete the unused "Data" volume, the best option is to erase the whole physical drive:

https://support.apple.com/en-us/HT208496#erasedisk


If you can figure out which volume to delete, then you will most likely want to rename them. To rename both the read-only system volume and the read+write "Data" volume you will need to do so from within Disk Utility. Just renaming the mounted volume from the Finder/Desktop will only rename the system volume. This post:

https://discussions.apple.com/thread/251461732#:~:text=converted%20for%20APFS.-,Open%20Disk%20Utility%20which%20will%20display%20both%20volumes%20in%20one,volume's%20name%20should%20change%20also.


explains to open Disk Utility and double-click on one of the volumes for which you want to change the name and edit the name. It should cause the other volume of the pair to be renamed accordingly. I suggest renaming the System volume to keep things simple. If you decide to rename the "Data" volume instead, then make sure to leave one of the " - Data" on the name.


Since you have a backup, there is limited risk to attempting to deleting one of the volumes and renaming the others as appropriate.


Nov 18, 2020 6:20 PM in response to HWTech

Thanks for the feedback, but what is unused is the current volume named Macintosh HD, not Macintosh HD - Data. The interesting thing is that the volume names in Finder are Macintosh HD and Macintosh HD - Data. But looking at the sizes with Disk Utility and Startup Disk, i can see i'm booted with Macintosh HD - Data and my data is actually on Macintosh HD - Data - Data.


The steps i'm contemplating are:


Delete Macintosh HD

Rename Macintosh HD - Data to Macintosh HD

Rename Macintosh HD - Data - Data to Macintosh HD - Data

Then set the Startup disk to Macintosh HD.


I think i'll wait for the long weekend to do this. It took nearly 18 hours to restore with Time Machine.

Nov 23, 2020 6:36 AM in response to JeffHouTX

Hi. I have two data "volumes" as well. To me this is a bug as the only solution is to erase my entire internal drive, then reinstall everything from a backup, something many users will have to deal with without knowing what to do next. My question is, can I copy all the data from the second Macintosh - data to the first, and then delete the second data "volume?"


Alternatively, what if I just leave the two data volumes in place. Is there any reason not to do this?


Thanks for your help (and letting me vent a little).


Ken Cohen


Nov 26, 2020 7:41 AM in response to HWTech

This worked. I took another backup, well several before i got it right, and waited until I had a few days off to do a restore if that became necessary. It was not. From the Disk Utility (in the running MacOS) I deleted the unneeded Macintosh HD volume and renamed the Macintosh HD - Data volume (the one with Macos on it) to Macintosh - HD. As you said, it renamed Macintosh HD - Data - Data back to Macintosh HD - Data. Then I rebooted without issue. No wipe and restore necessary. Thank you so much for your help and encouragement for me to take this path. I returned 11 GB to available storage!

Macintosh HD - Data - Data

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