Macintosh HD - Data and Macintosh HD2 both appear on my desktop, read/write

1) HD2, the one with the MacOS icon, is my CURRENT startup volume?

That's what it looks like from the screenshot.

2) I move everything of value into HD2, then I can remove the other volume in Disk Utility?

No, you move missing items from HD - Data into your home folder locations (/Users/yourshortname) of the startup volume.

The system files are the only thing on HD2 and you cannot write to it. Your data is stored on the Data volume that is attached to the System Volume (HD2 - Data). Everything on HD - Data should have been transferred into the HD2 - Data volume. But, you might want to check to make sure it did all get transferred and move anything that didn't (or you want). If you just copied the entire thing you would get a giant mess of duplicate files.

3) Will I have to be in Recovery Mode to do the removal, or can I do it from within my standard (HD2) login?

No, you can do so in a normal admin-capable login.

Jay Lender wrote:

Thank you. This is incredibly helpful. For what it's worth, I don't know how to pick a volume to start up with. I boot my computer, and what happens happens.

So, just to be clear...

1) HD2, the one with the MacOS icon, is my CURRENT startup volume?

2) I move everything of value into HD2, then I can remove the other volume in Disk Utility?

3) Will I have to be in Recovery Mode to do the removal, or can I do it from within my standard (HD2) login?

All Volumes share space within the Container with no penalty. You simple delete a Volume and it returns the stoarage space back to the Conatiner

references"

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

You can see what is mounted and what is not—

if you have Two Macintosh HD - Data

from Disk Utility.app you can see the mount point

One will be mounted at /System/Volumes/Data this is the one you want to keep,

*The other will be mounted at /Volumes and you can simply use the “ -“ to delete it.

Open disk utility and select each of the data volumes. The one that shows a house icon next to the name in the info pain is the current data volume. It should be the closest one to the OS volume.

For the other orphans that were left behind when you reinstalled, select each and click the remove volume button

Can you expand the two volume groups (click on the carrot next to each). I think you may cave two installs, but it has been a while since I looked at Catalina.

However, I do know you should not see both the System volume and the Data volume in Finder. They are confined into one.

What we may find is you have two installs, and we’ll have to make sure where all of your data resides before removing the old stuff.

So, you have to startup volumes, each with their own Data volume.

Figure out which one you want to use and startup with that.

The other Data volume will mount in the Finder. Compare its contents with what is in your home folder on the startup volume.

Move anything that was not copied.

Once complete, you can select the other volumes and Remove them.