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System data taking 170GB storage space

On my Macbook Pro (Monterey and also happened in Big Sur), System Data has reached to 165GB and it was 100GB only yesterday. I see on the internet that it normally takes around 15 to 20GB. What is the reason that this is so big and how can I delete the unnecessary files?


Posted on Oct 29, 2021 3:40 PM

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Posted on Oct 31, 2021 1:16 AM

After quite a bit of going through all the folders and files, I am convinced that these are the Library folders of apps like XCode which are quite big. I guess they are counted as "System Data". I cannot explain how it got 100GB bigger in 1 day but maybe they weren't indexed. Anyway, probably that is the disc space I have. Thanks for the help.


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Oct 31, 2021 1:16 AM in response to HWTech

After quite a bit of going through all the folders and files, I am convinced that these are the Library folders of apps like XCode which are quite big. I guess they are counted as "System Data". I cannot explain how it got 100GB bigger in 1 day but maybe they weren't indexed. Anyway, probably that is the disc space I have. Thanks for the help.


Oct 29, 2021 3:56 PM in response to murat_k

Unfortunately the macOS Storage Management section is known to be inaccurate when reporting on the space used by certain areas. It is hard to tell if this is the case or not.


Boot into Safe Mode which will take a bit longer to boot because it is running file system scans and it will delete some system temp & cache files.


Also some files may still be within an APFS system snapshot either from a macOS update/upgrade or from a pending backup. Make sure all your backups have completely transferred to your backup drive after which the backup snapshot should be deleted.

https://derflounder.wordpress.com/2018/04/07/reclaiming-drive-space-by-thinning-apple-file-system-snapshot-backups/


Dec 10, 2021 2:29 AM in response to murat_k

I had even bigger system data - around 620GB on a 1TB disk.


No way to shrink it. I then managed to shrink it by shutting down the Mac, booting into recovery, starting a terminal and disabling file system integrity protection:


csrutil enable --without fs


After a reboot, it kept shrinking and within minutes, the system data shrank to around 60GB.


Another shutdown, recovery, terminal and


csrutil enable


to re-enable file system integrity protection. Let's see if it will grow again.


Looks like the whole file system integrity protection is full of bugs. I had the issue that after a new install and a full restore of my time machine backup, the /Application folder was write protected so I couldn't install apps or updates any more. Apple support told me to erase my Macbook Pro 16 M1, re-install Monteray, use TM restore but without the Apps and then manually re-install all the apps.




System data taking 170GB storage space

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