Extra Macintosh HD data

Before reformat the parent drive and starting over (with adequate backups in hand)— did you try running First Aid on the Container, maybe it will detect an inconsistency here. From REcovery>DiskUtility.app>View>Show All Devices>

Ref your initial post: manually changing the volume names has added no clarity to the situation from my perspective.

The Cook wrote:

Just done a clean install of Catalina... When I looked at the HD it shows:

Macintosh HD

Macintosh HD Data

Macintosh HDData

Macintosh HDData —this is the anomaly here, and definitely shows using GB.

example ref.: from DU>View>Show All Devices>Container> in an effort to merge those two DATA volumes.

You can always wipe the drive and start over to get back to terra firm as suggested above by babowa.

Recovery: https://support.apple.com/en-us/HT204904

How to move your content to a new Mac https://support.apple.com/en-us/HT204350

How to use Time Machine to back up or restore your Mac: https://support.apple.com/en-us/HT201250

The Cook wrote:

I discovered why I had extra partitions.

on doing a clean install I forgot to erase hard drive. I ended up with two versions of everything.

All sorted now after doing it all correctly.

Many thanks for all your help.

Well that certainly explains it.

So you are saying the issue is solved.

You do not want to delete the data volume, see here

https://support.apple.com/en-us/HT210650

However, I am at a loss why you would have two - looks like a botched install. I'd try to erase and install from scratch using recovery. Make sure you have a backup.

The Cook wrote:

It’s the standard HD. Looks similar to your image. To be honest the extra drives showing up only take up 500MB but still needs removing.

500MB sounds like the Recovery volume got mis-labelled.

From the Terminal output from above you should see:

Catalina APFS container normally contains at least five APFS volumes:

• the read-only system volume, by default on the internal disk named Macintosh HD, which forms the root of the boot file system,
• the writable data volume, by default on the internal disk named Macintosh HD – Data, which is normally hidden from view at /System/Volumes and accessed via firmlinks,
• Preboot, a small volume of around 40-50 MB,
• Recovery, the Recovery Volume, of around 500 MB,
• VM, containing virtual memory caches, which is upwards of 20 KB depending on use.

Applications/Utilities/Terminal.app> copy and paste the following command line:

diskutil list

post the out put here.

I can say you do want to see both in Catalina, however yours something is strange anomaly and maybe a ghost.

From Disk Utility>View>Show All Devices:

being a iMac 21.5" 4K, is this a Fusion drive? has it been separated?

it would help to get a look, from the terminal.app copy and paste:

diskutil list

The Cook wrote:

This is what is showing.

to get it to back up I renamed the drives 1 and 2.

Applications/Utilities/Terminal.app> copy and paste the following command line:

diskutil list

I was hoping to get a better look from Terminal, something similar to :

% diskutil list     

/dev/disk0 (internal, physical):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *1.0 TB disk0

1: EFI EFI 209.7 MB disk0s1

2: Apple_APFS Container disk1 1000.0 GB disk0s2

/dev/disk1 (synthesized):

#: TYPE NAME SIZE IDENTIFIER

0: APFS Container Scheme - +1000.0 GB disk1

Physical Store disk0s2

1: APFS Volume Macintosh HD - Data 235.4 GB disk1s1

2: APFS Volume PreBoot 24.2 MB disk1s2

3: APFS Volume Recovery 525.9 MB disk1s3

4: APFS Volume VM 2.1 GB disk1s4

5: APFS Volume Macintosh HD 10.7 GB disk1s5