New disk partition created when OS last updated

My OS update was BigSur 11.0 to 11.1

Here is the disk layout from Terminal App

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *500.3 GB disk0

1: EFI ⁨EFI⁩ 314.6 MB disk0s1

2: Apple_APFS ⁨Container disk1⁩ 500.0 GB disk0s2

/dev/disk1 (synthesized):

#: TYPE NAME SIZE IDENTIFIER

0: APFS Container Scheme - +500.0 GB disk1

Physical Store disk0s2

1: APFS Volume ⁨Macintosh HD - Data⁩ 145.8 GB disk1s1

2: APFS Volume ⁨Preboot⁩ 348.2 MB disk1s2

3: APFS Volume ⁨Recovery⁩ 1.1 GB disk1s3

4: APFS Volume ⁨VM⁩ 20.5 KB disk1s4

5: APFS Volume ⁨LLLL⁩ 15.0 GB disk1s5

6: APFS Snapshot ⁨com.apple.os.update-...⁩ 15.0 GB disk1s5s1

Your Volume <APFS Volume ⁨LLLL⁩ 15.0 GB disk1s5> appears to be your Macintosh HD. I would not delete that.

ref: About the read-only system volume in macOS Catalina - Apple ...

Yours It is not a pristine presentation however it looks correct.

For a comparative reference only, a more pristine look:

MacBook-Pro ~ % diskutil list internal

/dev/disk0 (internal, physical):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *1.0 TB disk0

1: EFI ⁨EFI⁩ 314.6 MB disk0s1

2: Apple_APFS ⁨Container disk1⁩ 1.0 TB disk0s2

/dev/disk1 (synthesized):

#: TYPE NAME SIZE IDENTIFIER

0: APFS Container Scheme - +1.0 TB disk1

Physical Store disk0s2

1: APFS Volume ⁨Macintosh HD⁩ 14.9 GB disk1s1

2: APFS Snapshot ⁨com.apple.os.update-...⁩ 14.9 GB disk1s1s1

3: APFS Volume ⁨Macintosh HD - Data⁩ 279.7 GB disk1s2

4: APFS Volume ⁨Preboot⁩ 281.5 MB disk1s3

5: APFS Volume ⁨Recovery⁩ 655.5 MB disk1s4

6: APFS Volume ⁨VM⁩ 1.1 GB disk1s5

I may have lost the thread but if you are continuing to having issues— to wipe the slate and start anew,

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

Disk Utility>View>Show All Device it is here you select the parent Drive (not the Container level or Volume level.)

you erase/format/initialize the parent Drive and reinstall the macOS, and restore your user date from a backup.

Restore your Mac from a backup

The new drive icon, LLLL, is in a new location on my desk top each time I open my computer.

If this is your only issue, you do not have to show the Macintosh HD on the Desktop— it really is just a carry over from the old days. Make a change from Finder>Preferences>General> remove the Hard Disk selection

Larry Hendrickson wrote:

During the last update of Catalina OS, a "container" was created in my internal hard drive. A new drive, called LLLL, was created and the OS update placed in it. My old hard drive, MAC HD, is a second partition. Now all my library files are showing as being in both drives. The new drive icon, LLLL, is in a new location on my desk top each time I open my computer.

This structure is replicated of course on my backup drive.

I'd like to restore the original structure. How do I do that?

LL Hendrickson, Santa Barbara

Update from what to what "Catalina" a point update or a macOS upgrade...(?)

For a better look see

Post the output from the Terminal.app copy and paste:

diskutil list internal