After coming back from holidays I discovered that the TM hard disk I connect to my Mac has stopped mounting.

The HD was encrypted with FileVault.

I tried with Disk Utility to mount it but it does not work.

enter image description here

the diskutil mount /dev/disk3 hangs forever (1 hour then i stopped it)

running the diskutil repairvolume /dev/disk3

at some point it stops and gives these messages:

Load and verify Freespace Summary
Load and verify Block Accounting
Blocks on device E83429AA-8F51-4BB2-88CB-370A70F8003B are not accounted for by CoreStorage
Unable to bootstrap transaction group 30442: inconsistent crosscheck
No valid commit checkpoint found
The volume 17690DAF-921C-41DF-B225-3EAF5DF79F11 was found corrupt and needs to be repaired
Storage system check exit code is 1
Error: -69716: Storage system verify or repair failed
Underlying error: 1

What can I do to fix this?

1 Answer 1


Historically, the only thing I've ever known to be able to properly fix a…ermm… 'fnargled' Time Machine drive is DiskWarrior, but it's expensive for a one-trick pony & can only fix HFS, not APFS.
You might consider if there's anything on it you truly need, or to give it up & reformat.

The added consideration is what has caused the damage in the first place & is it time for a new drive? That's not really something you can properly test with it in its current state.

  • so the best thing is to wipe it out?
    – EsseTi
    Jan 12, 2023 at 17:10
  • You can wipe it and reuse the disk if the data is not irreplaceable, but if the disk is relatively old (>3yrs for a HDD) you might want to consider purchasing a new backup disk. You might want to consider purchasing two backup disks for redundancy.
    – IconDaemon
    Jan 12, 2023 at 19:39
  • I see, i may try to format it and if it brakes again i will buy a new one.
    – EsseTi
    Jan 16, 2023 at 7:49

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