MBP M1Pro Monterey: APFS Volume on Apple SSD internal disk does not self mount at startup

Instead of creating a new partition/APFS Container, you should have instead created a new APFS volume. An APFS volume behaves just like a partition, but does not require segmenting the drive into set sizes since people usually realize later on that one or both partitions is too small. An APFS volume can be mounted & unmounted if you wish just like a partition. The data stored on an APFS volume is separate from the other data in other APFS volumes even though all APFS volumes within a single Container share the storage pool.

Add, delete, or erase APFS volumes in Disk Utility on Mac - Apple Support

I have seen macOS have issues mounting external drives sometimes. Are you using any anti-virus software, cleaning/optimizer apps, or third party security software? These types of apps can cause all types of odd issues since they interfere with the normal operation of macOS.

Try booting into Safe Mode to see if you still have the same problem with auto mounting the other partition/volume.

You may also want to run Disk Utility First Aid on the physical drive, followed by running First Aid on the partition/Container you created which is having problems. Within Disk Utility, you may need to click "View" & select "Show All Devices" before the physical drive & hidden Containers appear on the left pane of Disk Utility. Even if the First Aid summary says everything is "Ok", click "Show Details" and scroll through the report to see if any unfixed errors are listed. If there are any errors listed, then run First Aid again until they are gone. If after several attempts the errors remain, then you will need to run First Aid while booted into Recovery Mode.

Is Filevault enabled on that volume?

If all else fails, then you can modify the instructions for preventing a volume from mounting automatically from this article:

Prevent a volume from mounting at startup - Apple Community

This is an old article referencing the HFS file system. An APFS volume is a bit more complex due to having a Container, but the basics are the same. You need to change "hfs" to "apfs" and "noauto" to "auto". Finding the UUID may be the tricker part.

Sartiniale wrote:

Thank you for the kind help.

I created a new volume, not a partition; anyway I will try this solution in the weekend. I will let you know!

Alessandro

FYI, The screenshot clearly shows you created a partition since the highlighted "Data HD" volume (disk3s1) is within a different APFS Container (disk0s3) than your macOS installation (disk0s2 & disk4).

Add, delete, or erase APFS volumes in Disk Utility on Mac - Apple Support

Partition a physical disk in Disk Utility on Mac - Apple

BDAqua wrote:

I'm worried why disk1, disk2, disk5, disk6, & disk 8 are missing!!!!!

"disk1" & "disk2" would have been utilized by the hidden APFS Containers "ISC" "disk0s1" & "Recovery" "disk0s4". Once macOS boots, those two Containers/volumes will be unmounted. The other ones you listed were probably other external devices which were ejected after "disk7" was connected.

You didn't partition it yourself did you???

I wonder why some drives are skipped there???

/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 disk5     1000.0 GB disk0s2

/dev/disk1 (external, physical):

  #:            TYPE NAME          SIZE    IDENTIFIER

  0:   GUID_partition_scheme            *1.9 TB   disk1

  1:            EFI EFI           314.6 MB  disk1s1

  2:         Apple_HFS SSD2          1.9 TB   disk1s2

/dev/disk2 (internal, physical):

  #:            TYPE NAME          SIZE    IDENTIFIER

  0:   GUID_partition_scheme            *28.0 GB  disk2

  1:            EFI EFI           314.6 MB  disk2s1

  2:         Apple_APFS Container disk5     27.6 GB  disk2s2

/dev/disk3 (external, physical):

  #:            TYPE NAME          SIZE    IDENTIFIER

  0:   GUID_partition_scheme            *1.9 TB   disk3

  1:            EFI EFI           314.6 MB  disk3s1

  2:         Apple_APFS Container disk4     1.9 TB   disk3s2

/dev/disk4 (synthesized):

  #:            TYPE NAME          SIZE    IDENTIFIER

  0:   APFS Container Scheme -           +1.9 TB   disk4

                 Physical Store disk3s2

  1:        APFS Volume Ventura - Data     455.1 GB  disk4s1

  2:        APFS Volume Preboot         2.1 GB   disk4s2

  3:        APFS Volume Recovery        1.2 GB   disk4s3

  4:        APFS Volume Ventura         9.3 GB   disk4s4

  5:        APFS Volume VM           1.1 MB   disk4s6

/dev/disk5 (synthesized):

  #:            TYPE NAME          SIZE    IDENTIFIER

  0:   APFS Container Scheme -           +1.0 TB   disk5

                 Physical Stores disk2s2, disk0s2

  1:        APFS Volume Macintosh HD      11.3 GB  disk5s1

  2:        APFS Volume Macintosh HD - Data   673.2 GB  disk5s2

  3:        APFS Volume Preboot         84.4 MB  disk5s3

  4:        APFS Volume Recovery        529.0 MB  disk5s4

  5:        APFS Volume VM           2.1 GB   disk5s5

You can use Drive DX to possibly get a better view of Drive health…

https://binaryfruit.com/drivedx

What drive is it running from?

In Terminal run this command & post the output...

diskutil list.

I'm worried why disk1, disk2, disk5, disk6, & disk 8 are missing!!!!!

Thanks!👍

Same issue and looking for solution too.