How to get rid of 174gb of "System Data"?

[memo90061]

Hello,

I've always struggled with storage in my iMacs. In the future I should buy one with at least 2tb. Anyways, when I check the system storage I have 173gb of system data. I've deleted so many files manually and used CleanMyMac X, but all of that system data is still there. What can it be? Should I start fresh? How would I start fresh? I have been using time machine. I think that's what caused huge storage problems in the past.

 

[throAU]

It's probably time machine local backups, and they're likely holding your deleted files until the space is required or you back up to external disk.

How to get rid?

They will purge if space is needed automatically, otherwise do a time machine backup to external media.

Or, read the tmutil man-page and remove them manually. But I'll leave that as an exercise for the reader; if you don't know what you're doing with time machine you probably shouldn't be doing it (i.e., if you go down this route read up on tmutil and what it does thoroughly first).

 

[Mike Boreham]

In Monterey Disk Utility provides the means to manage TM local snapshots without using Terminal.

Disk Utility now has full features for managing snapshots

 

[throAU]

In Monterey Disk Utility provides the means to manage TM local snapshots without using Terminal.

Disk Utility now has full features for managing snapshots

Nice! Didn't know that, and about time!

 

[Mike Boreham]

I meant to say that, as @throAU implies, TM local snapshots are not supposed to appear as used space in the storage chart or Finder. Most of the time they don't but unfortunately sometimes they do, causing unnecessary concern like yours.

 

[throAU]

They do usually appear as system used space in “about this Mac”.

But the tldr is don’t worry about the space consumed by system there. Once the system gets low on space it will start removing local snapshots to free space. Automatically.

 

[Mike Boreham]

They do usually appear as system used space in “about this Mac”.

But the tldr is don’t worry about the space consumed by system there. Once the system gets low on space it will start removing local snapshots to free space. Automatically.

I agree with your TLDR but not quite so sure about exactly what space is being released.

At this moment on my M1MBA:

Storage bar says System Data is 60.62GB

Storage bar free space is 214.2 GB
Finder free space is 214.2GB
Daisy Disk reports free+purgeable as 214GB

Disk Utility shows 24 snapshots use 13.04GB (select all, look at total size of selected underneath)
Daisy Disk reports the Snapshots are 13GB
CCC reports Snapshots as 12.97GB

So pretty sure "System Data" in Storage is more than just the TM Snapshots, but all is essentially purgeable in case of user need, as per your TLDR. Also pretty sure my systems have not always been as self consistent as this one currently is.

I know I have had incidents of extremely low free space being reported by Finder (I have not normally looked at About this Mac >Storage bar) and I have deleted Snapshots with CCC and seen a massive jump in free space to what I expected. Sometimes I have seen very low free space, not done anything, and it has corrected itself in a few hours, which I have attributed to Finder doing what I believe it is supposed to do, ie treat snapshots as free space because it can be used. These fluctuations have normally happened after deleting larger amounts of data.

Used and Free space reporting has become quite complex.