External SSD with Time Machine Failed to Mount - Unable to Unlock Disk

[appleuser21]

Hello everyone,

In November, I bought a brand new M1 MacBook Pro 16" along with an external SanDisk Extreme SSD for storage and Time Machine backups. Everything was working perfectly until two days ago.

First, I received a message that my Time Machine drive was full, but I ignored it because I knew that Time Machine automatically erases old backups to make room for new ones. However, yesterday, the drive failed to mount. It shows up in Disk Utility with its name, and when I try to mount it manually, it asks for the password but doesn’t accept it as valid.

I know the password is correct since I copy-paste it from a password manager app. Also, macOS used to mount it automatically on boot without any issues, so it definitely recognized the password before. Now, it suddenly doesn’t work, and I get the following error:

The disk "Time Machine" can't be unlocked. A problem was detected with the disk that prevents it from being unlocked.

Has anyone encountered this issue before? Is there a way to restore the drive without formatting it? And most importantly, does anyone know what might have caused this problem?

Thanks in advance for your help!

 

[BrianBaughn]

There's another thread on here about those devices:

https://forums.macrumors.com/threads/psa-do-not-buy-a-sandisk-extreme-portable-ssd.2433779/

 

[appleuser21]

There's another thread on here about those devices:

https://forums.macrumors.com/threads/psa-do-not-buy-a-sandisk-extreme-portable-ssd.2433779/

Thank you very much for your response. I'll look into it and hopefully I can return it.

Just to clarify: I had created two more partitions on this drive and those mount properly without any issues or data loss. Only the Time Machine partition was corrupted. That's why I was skeptical and didn't blame the disk at first.

 

[Fishrrman]

OP:

If time machine is failing on you, have you considered trying either CarbonCopyCloner or SuperDuper?

They won't "fill up" your drive with copy after copy after copy after copy of pretty much the same stuff...

Both are free to download and use for 30 days.

 

[wuchtbrumme]

reboot your Mac. Login. Disable standby for until this issue is resolved. Connect your SSD *with* the cable that came with it or better (same spec: USB3.2gen2 data). Then dont do anything. Let it complete the file system check (which is the reason why it was locked). It may take a day. If in Activity Monitor under all processes you no longer find the fsck, you can run First Aid from the Disk Utility. You can copy&paste here.
Then it should be working - or there is an unresolvable logic error in the data structure for the backup volume. The Sandisk defects usually are not on partition level, but on the hardware.

 

[appleuser21]

OP:

If time machine is failing on you, have you considered trying either CarbonCopyCloner or SuperDuper?

They won't "fill up" your drive with copy after copy after copy after copy of pretty much the same stuff...

Both are free to download and use for 30 days.

I've been using Time Machine for over 10 years now and this is the first time I've had an issue with my drives. I prefer Time Machine because it is built-in and I know it works great when I need it. Thanks for your suggestions though.

reboot your Mac. Login. Disable standby for until this issue is resolved. Connect your SSD *with* the cable that came with it or better (same spec: USB3.2gen2 data). Then dont do anything. Let it complete the file system check (which is the reason why it was locked). It may take a day. If in Activity Monitor under all processes you no longer find the fsck, you can run First Aid from the Disk Utility. You can copy&paste here.
Then it should be working - or there is an unresolvable logic error in the data structure for the backup volume. The Sandisk defects usually are not on partition level, but on the hardware.

I can't run First Aid because it has to be unlocked and it doesn't accept the password. The First Aid runs on the other partitions and doesn't report any problems.

 

[gilby101]

The First Aid runs on the other partitions and doesn't report any problems.

If you enable View > Show All Devices in DU's menu we can see the 3-level structure you have with Drives, Partitions/Containers, and Volumes. Without that DU just shows volumes.

It can help to first run First Aid on the drive, and then the partition/container, and finally the volume. You have only run it on the volume.

 

[Fishrrman]

"I prefer Time Machine because it is built-in and I know it works great when I need it"

Until... it didn't.
Hence, the reason for this thread.

That's why I suggest two 3rd-party products that DO work when you need them...

 

[gilby101]

Until... it didn't.
Hence, the reason for this thread.

I really think it is time you tried using TM again. It has changed since you gave up on it (in the late Stone Age ). So much more reliable now.

That's why I suggest two 3rd-party products that DO work when you need them...

I don't think other backup products will save you from the OP's issue with the disk being locked in some way.

ps. I use TM and (for its flexibility) CCC. Both seem reliable (both use APFS snapshots). TM is much easier to manage.

 

[appleuser21]

If you enable View > Show All Devices in DU's menu we can see the 3-level structure you have with Drives, Partitions/Containers, and Volumes. Without that DU just shows volumes.

It can help to first run First Aid on the drive, and then the partition/container, and finally the volume. You have only run it on the volume.

Thank you for this tip. I've enabled it and ran the First Aid on the drive with success:

Running First Aid on “SanDisk Extreme 55AE Media” (disk6)

Checking prerequisites
Checking the partition list
Checking the partition map size
Checking for an EFI system partition
Checking all HFS data partition loader spaces
Checking booter partitions
Checking Core Storage Physical Volume partitions
The partition map appears to be OK

Operation successful.

I think I'll have to format the partition, but I'm curious to find out what it might have caused this issue in order to prevent it from happening again in the future. I hope it isn't a hardware error.

 

[gilby101]

I've enabled it and ran the First Aid on the drive with success:

You should then run First Aid on each partition/container and finally on each APFS volume. Or, as you say erase the TM container.

Your drive layout looks a bit messy with two APFS containers and a third partition of some other format. If it were me, and I had backups of everything, I would start again - erase the whole drive creating a single APFS container and then create APFS volumes inside it. But I don't know your requirements - so do what works for you!

 

[Brian33]

I hope it isn't a hardware error.

This might sound silly, but in your third image in post number 10, you do realize the password it’s asking for is your Mac logon account password, and not the encryption password for the time machine volume?

It’s trying to access your login keychain, which contains the time machine volume password. I noticed in the image it looks like your login password is very long And started wondering if that’s your encryption password!