glyderfach wrote:
When I open Disk Utility, I seem to have two copies of Macintosh HD.
Under Container Disk 1, I have Macintosh HD (used: 11.19Gb, other volumes 200.31Gb) and another, Macintosh HD Data2 (used 195.2Gb, other volumes 16.3Gb). When I select 'Show in Finder' both point to Macintosh HD.
I think the second one was created when I did a complete reinstall of the OS.
Malware scans now take 11 hours
This is the new normal— you can read more on the two volume macOS—
About the read-only system volume in macOS Catalina - Apple ...
and yes Finder should see the two volumes as only one Macintosh HD
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If what you are saying is you ended up with two "Macintosh HD - Data" volumes, then this is an indication of an incomplete erase/reformat of the Parent drive before you did the re-install of the Catalina macOS.
Your way forward is Interent Recovery>Disk Utility>View>Show All Devices> it is here you reformat on the parent Drive level, not the Container level or the child Volume level.
How to reinstall macOS from macOS Internet Recovery - https://support.apple.com/en-us/HT204904
From Terminal you can get a good look, copy and paste:
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 11.1 GB disk1s1
2: APFS Volume Macintosh HD - Data 259.1 GB disk1s2
3: APFS Volume Preboot 80.8 MB disk1s3
4: APFS Volume Recovery 528.1 MB disk1s4
5: APFS Volume VM 8.6 GB disk1s5
MacBook-Pro ~ %