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User profile for user: ciaran law
ciaran law Author
User level: Level 1
10 points

error: underallocation detected on Main device

Hello,


I've got a mac mini late 2014. About 2 years ago after an update it started to run very slow. I've continued updating my computer since - running 11.5 now - but it always stays slow. I'm not sure why, but I ran First Aid on my Container Disk and it says that there is some issue, but I don't understand clearly what it is:


Verifying storage system

Using live mode.

Performing fsck_apfs -n -x -l /dev/disk0s2

Checking the container superblock.

Checking the EFI jumpstart record.

Checking the space manager.

Checking the space manager free queue trees.

Checking the object map.

Checking volume.

Checking the APFS volume superblock.

Checking the object map.

Checking the snapshot metadata tree.

Checking the snapshot metadata.

Checking snapshot 1 of 4 (com.apple.TimeMachine.2021-02-06-191525.local)

error: Cross Check : ExtentRef physical extent (46699019 + 8) has kind APFS_KIND_UPDATE but was not referenced previously

warning: Cross Check: Count not mark range (46699019 + 8) deallocated : File exists

error: Cross Check : Mismatch between extentref entry reference count (0) and calculated fsroot entry reference count (1) for extent (46699019 + 8)

Checking snapshot 2 of 4 (com.apple.TimeMachine.2021-10-14-195443.local)

error: Cross Check : Mismatch between extentref entry reference count (0) and calculated fsroot entry reference count (1) for extent (46699019 + 8)

Checking snapshot 3 of 4 (com.apple.TimeMachine.2021-10-14-205208.local)

error: Cross Check : Mismatch between extentref entry reference count (0) and calculated fsroot entry reference count (1) for extent (46699019 + 8)

Checking snapshot 4 of 4 (com.apple.TimeMachine.2021-10-14-215222.local)

error: Cross Check : Mismatch between extentref entry reference count (0) and calculated fsroot entry reference count (1) for extent (46699019 + 8)

Checking the extent ref tree.

Checking the fsroot tree.

error: Cross Check : Mismatch between extentref entry reference count (0) and calculated fsroot entry reference count (1) for extent (46699019 + 8)

Checking volume.

Checking the APFS volume superblock.

Checking the object map.

Checking the snapshot metadata tree.

Checking the snapshot metadata.

Checking the extent ref tree.

Checking the fsroot tree.

Checking volume.

Checking the APFS volume superblock.

Checking the object map.

Checking the snapshot metadata tree.

Checking the snapshot metadata.

Checking the extent ref tree.

Checking the fsroot tree.

Checking volume.

Checking the APFS volume superblock.

Checking the object map.

Checking the snapshot metadata tree.

Checking the snapshot metadata.

Checking the extent ref tree.

Checking the fsroot tree.

Checking volume.

Checking the APFS volume superblock.

Checking the object map.

Checking the snapshot metadata tree.

Checking the snapshot metadata.

Checking snapshot 1 of 1 (com.apple.os.update-E9AAB3EC1AEBCBE7B86B9E8051552B5B2FB97C31BD5426CC770E22722A03D8FC)

Checking the extent ref tree.

Checking the fsroot tree.

Checking the file extent tree.

Checking volume.

Checking the APFS volume superblock.

Checking the object map.

Checking the snapshot metadata tree.

Checking the snapshot metadata.

Checking the extent ref tree.

Checking the fsroot tree.

Verifying allocated space.

error: underallocation detected on Main device: (0x2c8920b+8) bitmap address (0x76ec1)

Space Verification failed.

The volume /dev/disk0s2 could not be verified completely.

Storage system check exit code is 0.


Operation successful.


Does someone knows what that mean and how I could fix the issues? Thanks


C.

Posted on Oct 14, 2021 7:52 PM

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5 replies
User profile for user: D.I. Johnson
D.I. Johnson
User level: Level 7
22,355 points

Oct 14, 2021 10:02 PM in response to ciaran law

I can't tell you what that underallocation error means, but it sounds like trouble and a job for Disk Utility First Aid.


NOTE: before doing this I advise you to make sure you have a current Time Machine or other backup of your user data.


Disk First Aid cannot repair the drive you are booted from. You'll have to restart you Mac in recovery mode and then use Disk Utility First Aid on the startup disk drive. To boot to recovery, press Command-R at startup and hold until you see the Apple logo and progress bar.

Use macOS Recovery on an Intel-based Mac - Apple Support


Once you are in recovery mode, launch Disk Utility. With DU running, click View > Show All Devices, then selecting the lowest indented volume of the topmost internal device, run First Aid. Run FA on each successively higher indented volume, then on the container and finally on the drive device itself.

How to repair a Mac disk with Disk Utility - Apple Support



Also, since performance of the machine is questionable and it is running very slow, I recommend that you run an EtreCheck evaluation of your Mac. EtreCheck is a diagnostic app that gathers important info about your hardware and software and reports it back to you. It is very highly regarded and meant to be used with Apple Support Communities to help others help you troubleshoot and resolve your Mac problems.


Please navigate to EtreCheck.com and download the free version of EtreCheck. Install the app and give it full disk access. Once you’ve run the app and created your report please post it with your reply to this message. 


You must upload the full report. To see how, please click >  How to use Add Text when posting… EtreCheck Report.


We can use the EtreCheck report to look for the more obvious things that may be causing your problem and advise how to correct them.

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User profile for user: ciaran law
ciaran law Author
User level: Level 1
10 points

Oct 15, 2021 3:26 PM in response to D.I. Johnson

Thanks so much for responding.


I've done further research and it seems that this issue was first detected after High Sierra OS moved all old HFS files to the new APFS. This makes sense because it's around the time of that update that my computer stopped working properly. Some complained about that, but Apple didn't offer a solution to fix the issue. My research has not uncovered any solution coming from Apple since High Sierra came out in fall 2017. From what I understand of the issue, during the upgrade to the new APFS format, space wasn't allocated properly on the SSD. So although my computer is less than 50% full, it is as slow as a computer filled to the brim.


Before I start implementing your recommendations, having a bit more background on what the issue could be, do you still feel that the process you recommend would be the best option?


Thanks again.


C.



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User profile for user: D.I. Johnson
D.I. Johnson
User level: Level 7
22,355 points

Oct 15, 2021 5:04 PM in response to ciaran law

You're welcome.


I understand what you're saying about the upgrade to High Sierra. Unfortunately, there is no way to repair the disk without either booting into recovery mode or booting from an external bootable drive. There's no guarantee that Disk Utility First Aid can fix the problem, but that is the only way you can try to run the First aid routines.


In fact, I wouldn't be surprised if DU First Aid can't fix the problem at all and you are then forced to wipe the drive, reformat and reinstall macOS in order to reclaim that drive space.


So yes, I do feel the process I recommend is the best option at the moment. As long as you don't allow the drive or any volumes to be deleted, erased, formatted or partitioned, then the process is nondestructive to your user data and files. And First Aid will either be able to fix the error or it won't.


As I mentioned, First Aid cannot repair the startup disk while you are booted from it. Boot into recovery mode and run Disk Utility > First Aid as I described previously. When the task is complete, reboot the Mac and check to see where things stand. If you are still unable to access the full capacity of the drive, it is then that you may have to exercise the option of erasing, reformatting and reinstalling macOS.


As for my suggestion of using EtreCheck, that is meant to address the slowness of the Mac. There are a number of reasons why your Mac may be so sluggish, and EtreCheck can help us identify obvious culprits in software or hardware. EtreCheck will have no bearing on the space allocation of your drive.


Finally, I do recommend that you make sure you have a current, up to date backup of your Mac before you do anything with Disk Utility. Just in case.

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error: underallocation detected on Main device

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