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I always thought any *nix-based system like OS X would be case-sensitive, although (just tested to make sure!) on Big Sur I cannot create 'FILE1' and 'file1' in the same folder, so it appears case-insensitive.

However, after it has formatted my backup drive, Time Machine only has a "case sensitive" option? The drive is shown at the top (as the external drive icon and title, not selectable, with only "Remove Disk" as an option) with the same Time Machine icon and same drive name beneath it, marked 'Case-sensitive'—I presume this is the usual interface and default choice?

After the first attempt, however, Time Machine fails (red question mark to right) and asks me to rename "one of the disks" (when there's only one connected) to a long string: "APPLE SSD APO512M Media - Data" although renaming it simply causes Time Machine to show two identically-named disks

Time Machine long backup name

However, after renaming to the string above and relaunching Time Machine, my renamed disk appeared twice (again) and on choosing the second case-sensitive (and only possible) option in the list of external disks the backup went ahead. Why the two identically-named disks, with one marked "case-sensitive"? After the first renaming from "backup| to the above, Time Machine showed the following:

Confusing external drive names

But "Backup" changed to the long name as soon as I selected "choose" for the second disk (with the long name) in the list.

I do a lot of web development on Linux servers, so I'm used to case-sensitivity, and I don't use any Adobe products (I understand they clash with case-sensitive drives) so what issues might I encounter with my separate but very similar backups from two non-M1 laptops running Big Sur or later?

diskutil list
/dev/disk0 (internal, physical):
   #:                       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 ⁨APPLE SSD APO512M Me...⁩ 563.2 MB   disk1s1
   2:                APFS Volume ⁨Preboot⁩                 313.4 MB   disk1s2
   3:                APFS Volume ⁨Recovery⁩                622.8 MB   disk1s3
   4:                APFS Volume ⁨VM⁩                      2.1 GB     disk1s4
   5:                APFS Volume ⁨APPLE SSD APO512M Me...⁩ 114.7 GB   disk1s5
   6:                APFS Volume ⁨APPLE SSD APO512M Media⁩ 15.3 GB    disk1s7
   7:              APFS Snapshot ⁨com.apple.os.update-...⁩ 15.3 GB    disk1s7s1

/dev/disk2 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *5.0 TB     disk2
   1:         Microsoft Reserved ⁨⁩                        134.2 MB   disk2s1
   2:                 Apple_APFS ⁨Container disk3⁩         5.0 TB     disk2s2

Without the external drive:

% diskutil list internal
/dev/disk0 (internal, physical):
   #:                       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 ⁨APPLE SSD APO512M Me...⁩ 562.8 MB   disk1s1
   2:                APFS Volume ⁨Preboot⁩                 313.4 MB   disk1s2
   3:                APFS Volume ⁨Recovery⁩                622.8 MB   disk1s3
   4:                APFS Volume ⁨VM⁩                      1.1 GB     disk1s4
   5:                APFS Volume ⁨APPLE SSD APO512M Me...⁩ 126.9 GB   disk1s5
   6:                APFS Volume ⁨APPLE SSD APO512M Media⁩ 15.3 GB    disk1s7
   7:              APFS Snapshot ⁨com.apple.os.update-...⁩ 15.3 GB    disk1s7s1

Running diskutil ap listgroups after removing the extra (case insensitive) disc via the Time Machine interface:

diskutil ap listgroups
APFS Containers (2 found)
|
+-- Container disk1 817F6958-3C62-4EDB-A445-A960AF3396E8
|   |
|   +-> Volume Group B696A136-89E9-4997-9E61-0061EC256CB0
|       =================================================
|       APFS Volume Disk (Role):   disk1s5 (Data)
|       Name:                      APPLE SSD APO512M Media - Data
|       Volume UUID:               B696A136-89E9-4997-9E61-0061EC256CB0
|       Capacity Consumed:         119796424704 B (119.8 GB)
|       -------------------------------------------------
|       APFS Volume Disk (Role):   disk1s7 (System)
|       Name:                      APPLE SSD APO512M Media
|       Volume UUID:               684AFD14-2E4E-4CDC-AD01-F8FC648F692A
|       Capacity Consumed:         15332147200 B (15.3 GB)
|
+-- Container disk3 D68F4756-2B56-47E9-8E3A-AF8F0F132ADD
    |
    +-> No Volume Groups among 1 Volume
daveeveritt@Daves-MacBook-Air ~ % 

Finally, what I see (I added comments about what each contains on Jean_JD's answer). I have no idea yet what my Time Machine backups contain:

enter image description here

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  • 3
    If I recall correctly you will find that the file systems on macOS are case preserving but not-case sensitive in the way that Linux/Unix is. As macOS is (for all intents and purposes) a consumer focused OS, I guess that Apple decided that most people don't understand that "aFILe" is not the same as "afile." I think there is an option to format a disk as "case sensitive" but you will likely find that breaks a lot of apps. Nov 23, 2021 at 13:21
  • 2
    Can you add to your question the results in text mode of the terminal command diskutil list?
    – user415185
    Nov 23, 2021 at 13:27
  • 2
    Default format is case-insensitive [though as Steve mentioned, case-preserving] but case sensitive can be chosen at format. The two don't mix well & case-insensitive is preferred unless you must have sensitive. i.stack.imgur.com/zX4Ef.png
    – Tetsujin
    Nov 23, 2021 at 14:21
  • There was no option for "Case insensitive"? @Jean_JD added above. Nov 23, 2021 at 19:09

3 Answers 3

1

I think the problem is a that you have two volumes named "APPLE SSD APO512M Media - Data" It's the message given by Time Machine.

I think this one is to delete :

 1:                APFS Volume ⁨APPLE SSD APO512M Me...⁩ 563.2 MB   disk1s1

You can verify by this command :

diskutil ap listgroups

The system group would be constitued by this two volumes :

   5:                APFS Volume ⁨APPLE SSD APO512M Me...⁩ 114.7 GB   disk1s5
   6:                APFS Volume ⁨APPLE SSD APO512M Media⁩ 15.3 GB    disk1s7

Data for disk1s5

System for disk1s7

If ok you can delete the excess volume :

diskutil ap deletevolume disk1s1

And after your Time Machine save should no longer be a problem

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  • I saw that, but I only have a single external drive plugged in? As soon as I started Time Machine, the "Backup" (which I'd named the external previously) and only two "APPLE SSD APO512M Media⁩" appeared, renamed as advised by Time Machine. Yet only one external drive is plugged in? Nov 25, 2021 at 14:35
  • Also, while Time Machine was "preparing" after the first attempt (which I think worked but no idea how to check) after the machine had slept, applications wouldn't launch, my machine froze and eventually I had to quit the Finder and force-shutdown, as it wasn't responding. After a restart I had to stop Time Machine and unplug the drive to get up and running again… Nov 25, 2021 at 14:40
  • 1
    Can you give the actual result of diskutil list internal ?
    – user415185
    Nov 25, 2021 at 15:12
  • added to my post above, without the external drive plugged in Nov 26, 2021 at 17:48
  • 1
    Happy for you. Just to verify, can you add to your initial question the actual result of diskutil list internal ?
    – user415185
    Dec 1, 2021 at 17:20
1

Do you see two "Data" partitions on Macintosh HD ?. If yes, this is causing the problem. Cheers.

enter image description here

(Dave): posting screenshot here, see comment:

enter image description here

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  • I do, but on opening them (right click, show in finder) despite the names in Disc Utility, one "APPLE SSD APO512M Media" contains the system and Applications installed globally, while "APPLE SSD APO512M Media - Data" contains my locally installed applications (via Homebrew). The External drive is also named "APPLE SSD APO512M Media - Data" because Time Machine requested it be renamed thus. It's hard for me to make sense of it, but the backup at least runs, although I have no idea what it's backing up, and I cannot open the Time Machine folders inside. Dec 3, 2021 at 14:17
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I have run in to the same issue. I have chosen the patrition (counting 831 KB) and actualy it was confusing the Time Machine. I removed it by clicking the minus sign and everything is back to normal again.

enter image description here

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  • interesting - things are definitely buggy. If I turn on auto backup, it goes into eternal 'preparing' and then all sorts of issues happen, forcing me to force-shutdown to get anything working again. Considering doing an online session with Apple help. Dec 7, 2021 at 21:48

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