Remove Macintosh HD Data volume after reverting from Catalina back to Mojave

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Remove Macintosh HD Data volume after reverting from Catalina back to Mojave

So I rather blindly upgraded from Mojave to Catalina as I usually do when a new OS releases, which of course rendered my Adobe collection and numerous other apps unusable. Lesson learned. So I downloaded Mojave to a formatted USB drive, rebooted the system using Recovery Mode and Disk utility, and erased the drive labeled "Macintosh HD" containing OS Catalina.

Or so I thought.

After rebooting again while holding down option, I selected the flash drive with the Mojave Installer. So now I'm back on Mojave, but now there's this secondary volume entitled "Macintosh HD-Data." And what's worse, both Macintosh HD and the Data volume only show 14 GB free of 120.47GB. What am I doing wrong here? I've already backed up all my important files and apps on an external drive, and I'm just trying to get to a clean, blank slate. Any help would be immensely appreciated.

13-inch Macbook Pro (Retina), early 2015, 120 GB, yadda yadda.

Posted on Oct 15, 2019 3:58 PM

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Answer 1

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Keanu D. Author

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Oct 15, 2019 7:49 PM in response to Keanu D.

Update: I think I was able to delete the HD-Data volume for good by highlighting it and hitting that little minus button up top. Not sure how I missed it. Anyhow I could just assume the 15.31GB still left there are just native apps or something, but that still seems a little large.

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Answer 2

Keanu D. Author

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Oct 15, 2019 5:29 PM in response to VikingOSX

Unfortunately, no I did not have a Time Machine backup on Mojave prior to the initial upgrade, but I did transfer all my files, applications, and data onto a secondary external hard drive.

Also for what it's worth, I just went and deleted the Macintosh HD-Data drive, but it simply reappeared again, but it looks as though much of my space has freed up. Now there's still an unexplained 15 GB or so of unknown storage that I can't seem to weed out, but I'll surely take that over 15 GB available. At this point I'd just like to know how to ultimately remove that and the HD-Data volume for good, but it sounds like I may need to cut my losses.

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Answer 3

Oct 15, 2019 4:53 PM in response to Keanu D.

Had you performed one last Time Machine backup of Mojave before upgrading to Catalina, and provided you did not reuse the drive as a Catalina Time Machine drive, you can boot into Recovery and select Restore from Time Machine Backup. That would have erased the entire drive, and then restored your Mac just as it was prior to the Catalina upgrade — including applications and user data. There would have been no Macintosh HD - Data upon completion of the Time Machine Restore.

Ask here before you walk into a mine field. If you do not have a Mojave Time Machine backup, you have a mess on your hands.

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Answer 4

Nov 11, 2019 8:11 AM in response to Keanu D.

Thanks Keanu. I'm going through this now as well. Downgrading back to Mojave after Catalina bricked several older 32-bit apps. The process back to Mojave has taken up most of my weekend. Not impressed with Catalina for several other reasons too.

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Answer 5

Keanu D. Author

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Nov 11, 2019 10:55 AM in response to luclatulippe

Hey Luclatulippe, since removing the HD-Data volume I've had no issues. I think it was automatically created by Catalina as part of its volume-sharing process, but if you've moved back to Mojave, it's essentially just an empty volume.

Also, for what it's worth I mentioned in another question that I spoke with a couple of Apple Specialists regarding the 15 gigs of used space and was told that it was (more or less) native system storage. Best of luck!

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Answer 6

soxrlow

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4 points

Nov 14, 2019 12:26 PM in response to luclatulippe

I had the same exact experience. I kept getting errors from Time Machine, which I think were caused by the multiple Macintosh HD Data volumes that Catalina created. Took several days to get everything restored to workable conditions.

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Answer 7

Dec 26, 2019 9:26 PM in response to Keanu D.

I had the same problem. I upgraded from Mojave to Catalina (solely so that my daughter could use PS4 controller in my Mac) and found my 32 applications would not work. Tried to restore Mojave using Time Machine and it failed - twice. Had to reinstall Mojave and found that since then I cannot use Time Machine. Then I discovered the HD-Data volume. I have very little free space now because of it. I think because Catalina upgrade created the HD-Data volume there was no longer enough free space left to restore from Time Machine. Its not that Time Machine did not work from the start. It spent hours trying to rebuild my original setup but then would stop 2/3rds of the way through. I think it just ran out of space. Originally I had close to 900gigs of free space prior to updating to Catalina. Now I have 40! I have backed up the HD-Date Volume and will the format that volume. Being a sucker for punishment I am going to attempt to create a dual boot Mojave /Catalina system for the sake of my daughter. :-)

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Answer 8

Keanu D. Author

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Dec 26, 2019 10:53 PM in response to Disgruntled Vista User

That sounds tedious indeed. Have you by chance come across this article for PS4 controller connectivity? I've been able to connect a PS4 controller since long before even Mojave, if memory serves.

https://www.techjunkie.com/ps4-controller-mac/

It certainly appears that the HD-Data volume remains as a residual asset even after reverting back to Mojave from Catalina. Hopefully no data loss or file corruption has occurred. And although I don't know your Mac's specifications, I might strongly suggest you ensure that PS4 controller connectivity is only possible on Catalina, given that PS4 controllers normally require a mere basic bluetooth connectivity.

I might also caution you to ensure that the games themselves are 64-bit and not 32-bit, as many Mac games are (I believe).

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Answer 9

Nov 11, 2019 9:12 AM in response to Keanu D.

Keanu did you notice after you deleted that volume if you experienced any problems? Did some applications disappear? Or stop working?

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Answer 10

Nov 11, 2019 4:06 PM in response to Keanu D.

Thanks! I've noticed that several older apps (probably the 32-bit ones) are in the "Data" volume but not in the main HD volume. I'll drag them into HD, delete "Data", reboot, and hope for the best.

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Answer 11

Keanu D. Author

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Nov 14, 2019 12:32 PM in response to soxrlow

Sorry to hear, hopefully no permanent damage was caused. I guess sometimes even Time Machine isn't the end-all solution.

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Remove Macintosh HD Data volume after reverting from Catalina back to Mojave

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