Why 2 drives on my desktop?

Hi,

Since Catalina released, macOS divide two partitions, one is read only system partition, Macintosh HD, the other is user level partition, named Macintosh Data for secures tighten against virus and malware.

I have had that issue as well.

It is definitely related to the new APFS file structure, and use of Time Machine for restore of accounts.

Here is what I have had success with:

Back up your Mac to an external Time Machine drive (and probably backing that up with a copy as well).

Then start up in in Recovery mode.

Erase the Internal drive using Disk Utility (choose APFS).

This will create the correct volume structure.

Reinstall an OS via Apple download to create a single clean account.

Once you are signed in on the new account, start Migration assistant, and choose your TM backup.

Note that if the new account is named the same as your old TM backup account, you will be asked for your password to approve merging the account with your TM backup of the same name.

Migration Assistant will then add all apps, user accounts, and docs from your last backup.

There still may be some minor settings to update (some Prefs, Apple ID, etc.), but almost everything will be identical to your old machine.

If the Clean account you created for the restore has a different name (and is not needed), it can be deleted later in Users and Groups / System Prefs.

You should show now two volumes in Disk Utility, but only one drive on your Desktop.