macOS Big Sur - First Aid fails on new APFS encrypted Time Machine backup disk

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Level 1

40 points

macOS Big Sur - First Aid fails on new APFS encrypted Time Machine backup disk

I just upgraded to macOS Big Sur and saw that it supported APFS formatted backup disks.

So, I thought I'd try it. I used an APFS formatted external 5 TB Disk. Then used Time Machine to set it as an encrypted backup disk. Then let the Time Machine backup process cycle through a few iterations and it all looked good - no obvious problems. However, I have had issues with Time Machine backups in the past so, to ease my mind, I ran Disk Utility First Aid on the Volume and it failed with the following:

Running First Aid on “Mac Backup 07” (disk3s2)

Repairing file system.
Volume is already unmounted.
Performing fsck_apfs -y -x /dev/rdisk3s2
Checking the container superblock.
Checking the space manager.
Checking the space manager free queue trees.
warning: Unable to read apfs keylocker ranges: No such process
Checking the object map.
error: failed to enable crypto I/O mode for container /dev/rdisk3: Resource busy
File system check exit code is 66.
Restoring the original state found as unmounted.
File system verify or repair failed. : (-69845)

Operation failed…

I have reformatted the backup drive and run through the whole process again but got the same result.

My alternate backup disk is an encrypted journaled HFS Plus volume and it passes First Aid with no errors.

I can't find anything about this error on the forums nor support pages.

MacBook Air 13″, 10.15

Posted on Nov 20, 2020 3:59 PM

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Answer 1

-MM-__

Level 1

16 points

Apr 9, 2021 10:05 AM in response to Polgs

As of today I see this same exact problem on my backup disk. SSD 256GB, formatted as APFS, encrypted. Big Sur 11.2.3 on a brand new Mac Mini with M1 processor. Time Machine seems to not see any problem with the disk, but First Aid gives me the same messages:

"warning: Unable to read apfs keylocker ranges: No such process"

and

"error: failed to enable crypto I/O mode for container /dev/rdisk5: Resource busy".

We need to know for sure whether our backup disk are reliable or not. This need to either be fixed or a statement by Apple that this error from First Aid can be ignored.

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Answer 2

EdAnson

Level 1

4 points

Apr 17, 2021 5:41 PM in response to Polgs

FWIW: I'm seeing the same problem on my TM server disk -- and TM is failing as well. It keeps cycling on "verifying backup...". When it gets to about 86% it stalls and then quits verifying. When I try to start a backup, it begins "verifying" all over again. I thought I'd check the integrity of the disk, but it starts to look like that's not an option.

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Answer 3

-MM-__

Level 1

16 points

Apr 18, 2021 4:21 AM in response to EdAnson

It is possible to use FirstAid on an encrypted TM backup disk if you do it from Recovery Mode (hold CMD+R at boot).

Just run the DiskUtility from the recovery screen.

On my system (MacMini, M1, BigSur), FirstAid has no problem checking *un-encrypted* backup disks. Please note that decrypting a disk with the Finder menu may take several hours. Worse still, if you ask Time Machine to do an *encrypted* backup, again, on a disk that you have manually decrypted, it will erase your old backup! With no warning whatsoever! Beware. I recommend to just go checking the disk from recovery mode.

I have not tried manually re-encrypting the backup disk from the Finder, instead of asking TM to reconnect the decrypted disk and make an encrypted backup. I do not know whether TM would accept an old backup that has been *manually* decrypted and then re-encrypted. Just asking TM to re-connect the old (and manually decrypted) backup disk and make an encrypted backup on it erased mine and made a new total encrypted backup. It took several hours and I lost all previous snapshots. (No big loss, in my case)

*MM*

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