I have been trying to use an APFS partitioned Samsung T7 shield 2 TB for a couple of weeks now but keep running into the same issue. After a few days of use, one of my partitions will no longer mount.

OS version: macOS Big Sur 11.7.4


  • All SSD partitions formatted as APFS
  • 1 TB allocated to file storage (archival)
  • 700 GB allocated to a Time Machine partition
  • 300 GB allocated for files in use at the moment (i.e. audio, video, documents etc)

The 300 GB Partition has been excluded from the time machine backup however the 1 TB partition is included in the backup.

Overview of formatted SSD

1 TB Archival partition details

Partition details (the one that is currently not mounting):

Partition info

What I have tried:

  1. Mounting using Disk Utility


    DiskManagement.disenter error 49218

    Disk Mount Error

  2. Repairing drive using first aid

    Results: Runs without error, exit status 0

    First Aid Results

  3. Killing FSCK process via terminal

  4. Repairing the volume through the command line

  5. Trying differently sized volumes

  6. Using volumes with size quotas instead of containers

In this instance it is the 1 TB partition that will not mount but I have also had it be the 300 GB partition (which is not included in the time machine backup).

The strangest thing to me is that even after erasing the whole SSD, and then re-adding the partitions. The issue still persists (regardless of whether I do or don't transfer any files onto the drive).

I have copies of most of the files stored on this SSD on a different drive so losing a couple things is not the end of the world but the frustrating thing is that this issue keeps returning.

Frankly I hope that I am just making a silly mistake and that someone will be happy to point it out. I cant say that I am very experienced or knowledgable in this field so any ideas or suggestions would be greatly appreciated.

  • 1
    Back up the drive, re-partition it and make one big APFS disk. Does the same thing happen? If it was a drive that you put into an enclosure your bought separately I'd say try another enclosure, but in this case, the nonsensical problems might just be a defective drive. Apr 18 at 23:03
  • Thanks for your suggestion. Gave it a shot but same as before sadly... Sending it back and going to get a new one. Hope that this fixes the problem.
    – Mushll
    Apr 19 at 23:09


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