backup fails with external volume mounted

On the extra volume that serves to expand the size of my MacBook Air (for the Photos Library) there are no Time Machine backups. I use other drives for that.

Am not busy emptying that extra volume so I can initialise it in the proper APFS format. See if that makes the difference.

A backup of the MacBook Air with the now APFS formatted external USB disk attached is now ongoing. Too early to tell if that made the difference.

Along the way I got convinced of the advantages of the APFS format. I needed some extra space to temporarily park the data before erasing and formatting the external disk. But on a 4Tb Time Machine and APFS formatted disk I could not write. Then I learned that I could easily create an extra volume for it which dynamically shares the space with what Time Machine uses on its side of the disk. Easy does it!

Unfortunately, formatting the external drive for APFS was not the solution.

2024-10-16 07:16:24  Failed to enumerate URLs under /Volumes/Seagate Expansion Drive for SnapshotStorage reuse with error Error Domain=NSCocoaErrorDomain Code=257 "The file “Seagate Expansion Drive” couldn’t be opened because you don’t have permission to view it." UserInfo={NSURL=file:///Volumes/Seagate%20Expansion%20Drive, NSFilePath=/Volumes/Seagate Expansion Drive, NSUnderlyingError=0x6000023cfb70 {Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"}}

is still the error that I get. In the user interface:

Both the backup drive and the extra volume are HFS+ formatted. "File system : Mac OS Extended (Journaled)" it says.

So you suggest to temporarily copy the contents of the extra volume to another one, format it to APFS and then put the temporarily saved content back?

Does the error indicate a hardware failure of the disk? "couldn’t be opened because you don’t have permission" suggests something with permissions.

I am hesitant to download software that comes as .zip from a company without an address or reputation.

In order to upgrade the formatting of my external disk to AFPS I moved all files to another disk and back after it became AFPS. Wouldn't that fix the permissions of the files?

I assume we are talking about permission issues of files on the external drive I try to include in the regular backup. Not the Time Machine destination drive. After all, without the external disk connected the backup goes flawlessly.

I could narrow down issues with certain files by excluding folders from the external drive! There are about 6 big ones besides the Photos Library. I start with excluding everything from the Time Machine options, except the Photos Library. Or if that gives a problem, just a backup of the newly created small text file not excluded.

Later tonight. To be continued...

Good news. Backup with just the Photos Library succeeded! So it's not the drive itself, the formatting, the hardware or anything. It is a permission issue in one of those folders that I excluded from the backup, undetected by Disk Utility.

But what that is and if a workable amount of files are the culprit I don't know yet...

Unexpected results all of a sudden. I thought I was on my way by excluding all the files and making a backup. Then including the Photos Library. More folders included, still no error. But then with some other folders included again the aforementioned error was back. Making a backup to another disk, (AFPS formatted!) also gave the error, even with all folders excluded except the Photos Library.

Trying to do it again to narrow done which folders gave errors. Each step takes many hours...

To one of the Time Machine backup disks with APFS (Case-sensitive, Encrypted). The default.

The other Time Machine disk still is Mac OS Extended (Case-sensitive, Journaled).

The external volume hooked up to the MacBook Air just APFS.

It should not matter because the issue is mainly with the combination of the Mac OS Extended Time Machine disk and the external volume.

A Time Machine backup to an AFPS volume that gave the error before did succeed after I quit the processes with 'Photo' in the name! Using Activity Monitor.

Now I still have to try if this was the obstacle for the other backup to the HFS+ volume. Did not have the time yet.

To complicate matters, I also excluded all suspect folders on the external volume. Except the folder with the Photos Library though.

The backup failed again during last night. In spite of excluding all the folders on the external volume except the Photos library.

I immediately went to Activity Monitor and there were 4 processes active with 'photo' in the name. Which I killed last evening before starting the backup.

So the problem seems to be that Photos starts up background processes which prohibit a backup of the external volume with the Photos Library.

How to proceed? I need to block those long enough for a backup to succeed...

I could also submit this as Feedback to Apple, but am I the only one with this issue? Perhaps n=1 and I should do some workaround.

Anyone? Help...