User profile for user: betaneptune
betaneptune Author
User level: Level 2
210 points

How to handle exit code 8 on First Aid check for TM volume while still functioning on iMac?

[...]

Checking snapshot 74 of 139 (com.apple.TimeMachine.2024-08-24-012921.backup)

error: (oid 0x15ef2aa) oms: btn: dev_read_finish(22999722, 1): No such file or directory

Snapshot is invalid.

The volume /dev/rdisk14s2 was found to be corrupt and cannot be repaired.

Verifying allocated space.

The volume /dev/rdisk14s2 could not be verified completely.

File system check exit code is 8.

Restoring the original state found as mounted.

File system verify or repair failed. : (-69845)


Operation failed…


But it appears to work fine. I retrieved (restored) a test file using "Enter TimeMachine".


Should I run First Aid on the container before deciding what to do? (If successful, will probably take maybe 24 hours or a few more!)


I'd like to copy the backups (snapshots) off, but I don't think there is a way to do that.


Recommendations?

Should continue to use this disk?

Re-init it (Erase it and start again)?! OTOH, I don't want to lose the existing backups.


BTW, I did have some trouble with this disk earlier. A certain file on the 2023-08-22 backup was fine, but in the succeeding backup, dated 2023-08-29, it was corrupted! But on my other TM disk, it was still fine! (I think the file might have gotten corrupted on the internal (Startup) drive! But the corrupted snapshot (see above) is not either of those. I still don't know why the change was picked up on disk 1 but not disk 2. These are hard drives (spinning platter and all that).


TIA!


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BONUS:

Tip:

I would get the infamous exit code 65 on this. But if you power the disk on after the boot is complete, it works! Maybe dismounting it, then pulling the USB cord out and in is sufficient.





[Re-Titled by Moderator]

iMac 24″, macOS 12.6

Posted on May 13, 2025 10:56 AM

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User profile for user: betaneptune
betaneptune Author
User level: Level 2
210 points

May 18, 2025 11:31 AM in response to HWTech

@HWTech


Ran Disk Utility First Aid (DUFA) overnight on the container. Same thing!


OK, the disk is bad, except that I can still read it fine, both in the Finder and in Time Machine. And I can restore from Time Machine. And there are backups after this date that work fine.


Two questions:

  1. Do I really need a new disk? Might erasing the disk and starting over work?
  2. How do I copy backup snapshots off of it? Last I heard, it's impossible.


TIA!


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User profile for user: VikingOSX
VikingOSX
User level: Level 10
120,677 points

May 13, 2025 11:15 AM in response to betaneptune

Boot your Mac into Recovery mode before running Disk Utility First Aid on the Time Machine drive. No operating system process should be accessing that Time Machine drive when performing First Aid on it and that can only be the case in Recovery mode.


How to start up from macOS Recovery - Apple Support


The other thought I had was that a 16 TB OWC drive may need a firmware update if OWC support suggest this. Call them.


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User profile for user: betaneptune
betaneptune Author
User level: Level 2
210 points

May 14, 2025 2:08 AM in response to VikingOSX

I will call OWC. But note:


From Repair a storage device in Disk Utility on Mac - Apple Support


"Note: If you’re checking your startup disk or startup volume, restart your computer in macOS Recovery,

select Disk Utility in the macOS Recovery window, then click Continue."


If you run FA on a non-startup disk, the disk is dismounted and allocated to the FA process. Nothing else can touch it. If it could, that would be pretty poor for "the most advanced operating system in the world," well, as they at least used to call it.


FA runs fsck. And on OpenVMS systems, it was easier. The command was ANALYZE/DISK_STRUCTURE (you only need to type enough chars to make it unique). You dismount the disk. Allocate it to yourself. Mount it private. Run the ANA/DISK command. (I'd include the L, but I don't want to get in trouble.) Error messages either make sense or can be easily looked up in a single book, or perhaps even with the HELP/MESSAGES command. Not the case with at least some other operating systems.

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User profile for user: betaneptune
betaneptune Author
User level: Level 2
210 points

May 13, 2025 11:29 AM in response to VikingOSX

Yes, I don't get the exit code 65 in recovery mode, but other disks (except the Startup drive) work fine with the machine up. I recently ran FA on my other backup drive with the Mac up and it worked fine. During the FA run, the disk is not mounted for the system. FA has it all to itself. Actually, you can even run FA on the startup drive while the Mac is up, but it will freeze the system. Running in recovery mode requires a camera to record the results.


Also, I really don't want to have my Mac unavailable for over 24 hours if I can help it.


Again, FA works fine on all my external drives. I assume this error is legit. I ran FA twice on this disk, and twice got the same error on the same snapshot each time. Mostly I just want to keep the backups for the 2023-08-22 and 2023-08-29 runs, just in case I later find something that can explain why the corruption was picked up, and why it wasn't on the other TM drive. Also, I'd rather not have to buy another 16TB drive!

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User profile for user: HWTech
HWTech
User level: Level 9
65,102 points

May 13, 2025 6:20 PM in response to betaneptune

Personally I would check the health of the drive if OWC allows access to the drives' SMART health attributes. Some OWC enclosures allow it while others do not. If the enclosure is a multi-drive or RAID enclosure doesn't have its own web interface or software to manage the enclosure, then you can just try using DriveDx (free trial period) to check the drive's health. You may need to install a special USB driver to access the external drive's SMART health information if the enclosure allows it.


For Hard Drives....any "Warning" or "Failing" notices in DriveDx indicates a worn out or failing Hard Drive respectively. I consider both fatal with the drive needing to be replaced. SSDs are another matter & require a manual interpretation of the health information.


Feel free to post the complete DriveDx text report here using the "Additional Text" icon which looks like a piece of paper on the forum editing toolbar. Or if the enclosure has its own monitoring interface, post a screenshot or report of that enclosure report here for review.


If the Hard Drive(s) show as healthy, then it is hard to say whether it is safe to continue using the TM backup. Theoretically those file system errors should be restricted to just that snapshot/bundle, but since TM has so many links to make TM work it is hard to say whether it would be a problem for accessing the good snapshots/bundles. Theoretically at some point TM will delete the older backups once the TM drive fills up & getting rid of those errors, but if you have a very large TM drive, but only backing up small amounts of data, then that TM drive may take a long time to fill up.


To err on the side of caution it may be wise to get another drive for TM and keep this one as a secondary backup or to keep older copies of your files for a while if you wish, otherwise you can try erasing the TM backup drive (assuming the drive is healthy) and see what happens. Having a new TM drive may still be a good idea anyway even with that option.

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How to handle exit code 8 on First Aid check for TM volume while still functioning on iMac?

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