"System Data" consumes 142 GB of space – unable to figure out why

[redheeler]

I've not been able to figure out what's using all this space on my 256 GB Mac mini.

Even starting from the root of the drive and selecting everything with Command-Option-I (my standard way of disk space troubleshooting on Mac) the total usage is not even close.

It isn't APFS snapshots either as far as I know, I haven't seen any show up in Disk Utility. Also tried disk repair and it found no issues.

Anyone have any ideas what's going on or how to fix other than delete and reinstall my entire OS?

 

[baconcat_8964]

macOS categorizes all application data that is not correctly placed in its dedicated folder as "System Data".

I would recommend using applications such as GrandPerspective to thoroughly scan your drive and identify which folders or files are taking up siginificant space.

 

[redheeler]

I finally freed up just barely enough space to update my MacOS and after the update the "System Data" is only 51.66 GB. That's crazy... I was on 15.1.1 before and now on 15.4.1. (And yes I had tried system restarts before as well)

This is definitely some kind of bug with MacOS then. I can live with Apple selling Macs with 256 GB SSDs but I can't live with bugs that use up more than a third of that space for no reason. I hope I don't run into it again.

 

[gilby101]

I can live with Apple selling Macs with 256 GB SSDs but I can't live with bugs that use up more than a third of that space for no reason

Well, I couldn't live with a 256GB Mac. I also put some effort into discovering what is consuming disk space, which does not seem to be a bug - it is design.

DaisyDisk https://daisydiskapp.com/ is the best app for getting to grips with what is consuming space. Even then you will have to understand snapshots, etc.

 

[Bigwaff]

This is definitely some kind of bug with MacOS then. I can live with Apple selling Macs with 256 GB SSDs but I can't live with bugs that use up more than a third of that space for no reason. I hope I don't run into it again.

Ain’t a bug, just extremely poor design and execution. (Perhaps one can consider such a thing “a bug”…). Either way, you will run into it again.

What is System Data in Storage Settings?

The bar chart in Storage Settings shows most of your startup volume is full of System Data. What does it mean, and what use is it? Is its measure of used and free space accurate?

eclecticlight.co

 

[redheeler]

Ain’t a bug, just extremely poor design and execution. (Perhaps one can consider such a thing “a bug”…). Either way, you will run into it again.

What is System Data in Storage Settings?

The bar chart in Storage Settings shows most of your startup volume is full of System Data. What does it mean, and what use is it? Is its measure of used and free space accurate?

eclecticlight.co

I'm not referring to the ambiguity of the "System Data" category but rather how much total space was used on my drive before and after the MacOS update being massively different for no explainable reason. (The storage settings just put all that additional usage under "System Data").

It could be system log files or caches of some kind that the MacOS update cleared, but those should not under any circumstances take up 90 GB of storage space. I'd absolutely call that a bug.

 

[nmt1900]

This thing has more than one bug in it. I have to keep Apple Intelligence enabled - disabling it causes system data calculation to fail and big amount (exceeding the amount of system data) of used storage gets marked as purgeable. Problem disappears after enabling Apple Intelligence. There are some claims about this being a known issue and only workaround being complete wipe and reinstall from scratch.

I do understand that my case is somewhat different but this is just to describe how bugged this part of system really is at the moment...

 

[Fishrrman]

I've posted in the forum numerous times:
The "Storage" pane shown above is often unreliable, and unusable.

If you want to see what's using up disk space, use other means (3rd-party apps).