How to delete "other volumes in container"

When you erased the APFS volume when performing the clean install of Mojave, you should have instead erased the "Fusion Drive" item which would have destroyed all the extra APFS volumes used by macOS 10.15+ which includes the "Data" volume. The "Data" volume was used with Catalina and is not used in older versions of macOS such as Mojave. As long as you have a backup of the data located on that "Data" volume, then you can just delete the "Data" volume using Disk Utility. See this Apple article for instructions:

Add, delete, or erase APFS volumes in Disk Utility on Mac - Apple Support

Don't try deleting anything until you find out what they are. The Other Volumes may be left over from your Catalina install (or maybe not) ... but they need to be clearly identified before doing anything about them. Even if they are left over from Catalina, it's necessary to be very cautious before removing any of them.

If you are comfortable using the Terminal app, open a session & enter this command:

diskutil list

It will provide details about your drive(s) and volumes. Post a copy of the results here. People will weigh in on what the Volumes are and what may be done about them.

BTW, get rid of Clean my Mac. It will end up causing you more problems than it ever claimed to solve.

The drive layout & configuration associated with macOS 10.15+ is complicated. The "Macintosh HD" volume contains the macOS system files on a read-only volume. The "Data" volume or "Macintosh HD - Data" volume is the volume which contains the home user folders (all your documents) & modified system configuration files. With macOS 10.15+, these two separate APFS volumes are linked together behind the scenes to appear as one single volume called "Macintosh HD" like all version of macOS 10.14 & earlier used. Apple tried to make the new complex layout look & behave exactly like it did prior to macOS 10.15. However, Apple wasn't entirely successful.

Normally older versions of macOS will just see those other APFS volumes as independent volumes, although the root of those two APFS volumes will contain the same folder structure.

I'm not sure how you restored the data from the TM backup, but if you happened to be booted from macOS 10.15+ (perhaps in Recovery Mode), then it probably restored the items to the other APFS volume since TM does not automatically restore while booted to an older version of macOS (you can do that manually).

Keep in mind the "Data" volume contained the macOS 10.15 home user folder which contained all your old documents.

We cannot really be sure since we cannot see the system first hand.

Like I mentioned before, if you have a copy of all your data and the data stored on the other APFS volume, then while booted to the internal drive, use Disk Utility to delete the other APFS volume. macOS should not allow you to delete an APFS volume associated with the OS you are currently booted. If you have good backups, then there should be very little risk.

I'm actually surprised there is no "Update" volume shown in the output of from the "diskutil list" command. macOS 10.15 Catalina actually had an "Update" volume unless a later macOS 10.15 patch changed this into a snapshot so it is no longer seen as an independent volume.

The only way to have a clean Mojave installation is to erase the whole Fusion Drive item followed by reinstalling macOS Mojave, then somehow restoring your files from the backup (likely would need to launch TM app & navigate the backups from the TM app so you can restore particular folders & files manually).

It is really hard to advise you any further because it really requires being able to see & interact with the system which we cannot do. If you feel you have a good backup and a copy of all the files located on the "Data" volume, then delete the "Data" volume using Disk Utility while you are booted into the OS of your internal drive. That is the easiest & quickest option, otherwise you would need to start over completely by erasing the Fusion Drive item.

This looks like a normal Mojave installation on a Fusion drive to me. All the volumes are the usual ones, nothing amiss.

You said you had a big loss of space ... how much free space did you previously have, or were expecting to have after your reinstall?

You have 760 GB used in Macintosh HD, this is the volume that contains macOS & embedded apps. It seems large to me.

You have 2.1 GB used in Macintosh HD - Data, which is the volume containing user-installed apps & all your user data. Is this more than you expected it to have?

Next step would be to examine what's taking up space on the drive. Are you using any apps that have libraries ... Music, TV, iMovie, Photos, Final Cut, Lightroom, CaptureOne, Premiere, etc. Do you have backups of any iPhones or iPads? All can take up significant amounts of disk space. You could use Daisy Disk or similar utility to identify what's taking up space on the disk. (It's available in the App Store as well as directly from the vendor.)

gerrymoffett wrote:

I had 1.3TB before the Catalina install I have also noticed the Mac HD data disk is on my desktop which has never been there before and it is partially the same as my Mac HD and I don't have any Music, TV, iMovie, Photos, Final Cut, Lightroom, CaptureOne, Premiere, etc.

New information here. The Macintosh HD - Data volume should not be visible on the desktop. Coupled with your report of storage space loss it appears something is wrong. My guess is it has something to do with downgrading back to Mojave. It's beyond my skillset to pursue this further, but I will alert colleagues who have more experience with this - hopefully they will pop in to help you.

ps. In Daisy Disk, I hope you discovered that as you hover the mouse over different segments of the disk display, it will identify the folder or file that each area represents. It's helpful in tracking down large folders/files.

Thanks for the update. We're glad everything is good.

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