Object Map Invalid on APFS drive. Options? Sign of drive dying?

Discussion in 'macOS' started by parkds, Apr 22, 2019.

  1. parkds macrumors 6502

    Jan 23, 2003
    Moderators, not sure if this is the correct place for this; feel free to move if needed.

    I recently noticed several files / apps had disappeared from my iMac's boot drive. At the same time, my Backblaze cloud backup locked because it detected too many file changes. I ran Disk Utility and found the drive's Object Map is invalid (the drive had been converted to APFS when the machine was updated to Mojave).

    Of course Disk Utility can't repair the Object Map (why can't Apple's tools recover a file system when they aren't sharing details of it with 3rd parties!). And from looking online, without 3rd party software being available it seems my only real option is to wipe the drive, do a clean system install, and restore from a backup.

    Restoring from Time Machine takes forever so I want to make sure I am being smart about this. Are there any other options forward other than wiping the drive? Is there software I am not aware of that can repair this?

    Also is the Object Map randomly corrupting simply bad luck or a sign that my internal drive is dying? I was planning on a new computer purchase within the next year and I am reluctantly happy to speed up my timeline if it prevents this (or something worse) from occurring again in a few weeks.
  2. treekram macrumors 68000

    Nov 9, 2015
    Honolulu HI
    It would help to know what year iMac you have; what type of disk you have (HDD or SSD); if it's a fusion drive or not; and what version of Mojave are you using?

    I would not do any more TimeMachine backups until your situation is resolved. I would suggest doing a backup of what you have now using Carbon Copy Cloner or similar software. "CCC" is free for a trial period. If you do use CCC, turn off the snapshot feature. This would obviously require an free disk or partition equal to or larger than your iMac disk. It doesn't have to be formatted as APFS to be used.
  3. chown33 macrumors 604

    Aug 9, 2009
    It could be a sign of any component in the data transfer chain failing. This includes cables and connectors.

    It could also be a sign of operational failures, such as crashes due to power loss that thereby lose or corrupt data, where the power loss could be prevented or mitigated by something like an Uninterruptible Power Supply.
  4. parkds thread starter macrumors 6502

    Jan 23, 2003
    Thanks for your responses! I have a 2013 27" iMac with a 3TB Fusion Drive that was automatically converted to APFS during my upgrade to Mojave.
    Prior to noticing the issue with my internal hard drive this week, the computer had not suffered any unusual crashes or power disruptions.

    I have cloned my hard drive using CCC and plan to use the Time Machine backup I have. If there is an issue with that, I will investigate the APFS snapshot I guess. I just want to avoid going through all of this again in a few weeks if this is a sign of something more serious coming (I know very little about APFS and it's warning signs vs my experience with HFS+).
  5. treekram macrumors 68000

    Nov 9, 2015
    Honolulu HI
    My best guess would be it's an issue with APFS and a fusion drive. Apple probably still has some kinks to work out in this regard. If APFS and a fusion drive presented no issues vs. a stand-alone SSD, it would have been available with High Sierra, but it wasn't. This is why I asked what version of Mojave you have - hopefully Apple has improved APFS with fusion with time. I see less reports of APFS corruption-type issues here on macrumours.com as Apple releases new OS updates.

    It could also be a chance combination of factors that will never occur again or it could be natural degradation of the HDD, SSD or some other hardware in your system - it's not easy when something like this happens just once. Well, maybe Apple knows but they aren't likely to disclose this.

    What you could do is get software that reads the SMART attributes of the SSD and HDD, but you have to take the results and any software that attempts to interpret the results with a grain of salt. If you want to get this software and present the results, that's fine but unless the results are on the extreme side, they probably will not help much in determining the life span of either your SSD or HDD. The interpretations of SMART results by apps that have been presented on these forums tended to be over-reactions, IMO. So if you do this, beware of this.

    Your HDD, if original, is old but because it doesn't bear the full brunt of being a system disk (because it's part of a fusion setup), it maybe OK. The SSD's that Apple uses for this model of the iMac were probably pretty good (I saw a Samsung in one teardown on the Internet) so even though it's only 128GB and sees a lot of erase/write cycles, it wouldn't surprise me if there's still a lot of life in it.

    So possibilities, but no clear answer.

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4 April 22, 2019