System Data HUGE - 700GB. Help!

[jonblatho]

More specifically, neither me nor Apple can find the data......and, therefore, cannot delete it. Even going into all the "hidden" folders, nothing anywhere adds up to 661GB of data.

So, no. There is no error because it can't be found.

The TimeMachine snapshots that are showing add up to a little over 13 TB. So, those can't be sitting on the 1 TB SSD.

With all due respect, did you read the thread?

APFS snapshots aren’t files. They’re effectively lists of file diffs (along with metadata like file size). The snapshots themselves are small, but Time Machine keeps these local snapshots/lists and keeps the underlying files around in APFS, even if they appear to have been deleted, in case you need them when your backup location is unavailable. This is why you can appear to have many terabytes’ worth of snapshots on a 1 TB SSD. As Apple’s documentation and comments here have noted, these snapshots are local to your device and completely unrelated to your Time Machine backups stored elsewhere.

APFS snapshots do not show up as regular files, which is exactly why you can’t see any data adding up to 600+ GB in the Finder.

Especially during times of great file churn (like a bunch of big app updates), snapshots will grow in size because the diffs get larger. The system is supposed to automatically purge APFS snapshots when they’re over 24 hours old or disk space is needed. This doesn’t always happen in practice, in which case you must delete the snapshots manually (instructions for which are earlier in the thread).

I agree that you shouldn’t have to wipe the machine, which is why I and others have suggested that you try deleting the APFS snapshots first.

 

[Ben J.]

Again:

View APFS snapshots in Disk Utility on Mac

In Disk Utility on Mac, view a list of APFS snapshots, copy information about the snapshots, and delete them.

support.apple.com

And:

About Time Machine local snapshots - Apple Support

Time Machine lets you restore files from local snapshots of the files on your Mac, even when your Time Machine backup disk isn't available.

support.apple.com

 

[Admiral]

I have backups to TimeMachine on a NAS (QNAP).

BTW - I am a certified IT Pro (A+, CCNA, Security+, MCSE, Cloud+, CISSP and PMP) - 31 years as an IT Director.

With respect, these two statements are incongruous to me. But hey, looks like you've got this well in hand, champ.

 

[conmee]

Have you tried running Onyx? Run Maintenance with the preselected options. I use iCloud and toggled off Optimize Storage since I have a 2TB SSD and I didnt want to give iCloud the option of only keeping files in the cloud even though it says it will only do that if I am low on space. Anyhow just switching that off my System Data jumped from 22GB to 280GB (MBP M5). So then I switched back to Optimize Storage, rebooted, and it was still 280GB. So I ran Daisy Disk and it didn’t show anything in the 280GB range and System Data according to Daisy Disk was still around 28GB. I ran the default Onyx Maintenance routines which then reboots the system, and when I checked again the System Data was back down around 22GB.

I think in general I don’t 100% trust the values macOS gives me in the Storage settings. They sometimes differ from what I see in Disk Utility and tools like iStat Menu and Daisy Disk.

Anyhow, if Apple can’t figure it out after 3+ hours dinking around, time to nuke your system from orbit. It’s the only way to be sure. 😉

 

[Fishrrman]

jonblatho commented:
"I agree that you shouldn’t have to wipe the machine, which is why I and others have suggested that you try deleting the APFS snapshots first."

Your point is well taken.
OP should try your suggestion first.
BUT...

If that doesn't seem to work for him, I suggested (in reply 22) that he use the "erase all content and settings" option BECAUSE it works quickly and smoothly.

BUT HE MUST HAVE A GOOD BACKUP.

I don't know how much personal data is on the OP's internal drive, but if it's not too much, the erase/restore shouldn't take very long at all.
The "erase all content" and "restoration" to "moment zero" goes very quickly. I report this from my own "test experience" using a 2021 MacBook Pro (m1pro).

Then, the migration from my backup drive (during the once-again-initial-setup) went fast as well (because I don't keep a lot of stuff on the MBP).

If the OP has many GB's of stuff from his backup, well... then it will take a little longer.

I suggested creating/using a cloned backup because I believe those actually migrate faster than a tm backup...

Finally, the reason to use the "erase all content and settings" is because -- like conmee quips about in the reply above this one -- "nuking it from orbit is the only way to be sure" ...