System Data Huge (410GB) On M3 MBA

[Buadhai]

My wife has an M3 MBA Running 26.1 with a 500 GB Internal SSD.

She was having trouble backing up and when I checked I was shocked to see that her System Data is just over 410 GB. (On my M2 MBA it is only about 48GB.)

I've searched around and find very little on what to do about pruning this down to a reasonable size.

I have emptied the trash which had zero effect. I ran Disk First Aid which found no errors and had no effect on the System Data size.

~/Library/Caches take up less than 2GB as does /Library/Caches.

Any ideas?

 

[Slartibart]

Local Time Machine Snapshots? For detailed insight and clearance run e.g. Omni’s DiskSweeper, Disk Inventroy X, or VizDisk (all free, other programs are available 😁)

 

[gilby101]

She was having trouble backing up and when I checked I was shocked to see that her System Data is just over 410 GB

Is that with Time Machine? That can be both a cause or a symptom for large System Data.

In Disk Utility:
Select the system "data" volume labelled with a trailing " - Data".
In the menus, View > Show APFS Snapshots
You should now see an entry for up to 24 snapshots all created in the last 24 hours.
Right-click on one of the column headers and make sure "Private Size" and "Cumulative Size" are enabled.
Wait for it to fill out all the numbers.
Are any of the Private Sizes or the (cumulative) Sizes very large?

If these snapshots are all in the past 24 hours but a one or more is very big, just be patient as TM will remove the snapshots by tomorrow.

 

[gilby101]

If you need to scan the whole disk, use DaisyDisk (free trial, but you need the paid version) which allows you to scan "as Administrator" so that it is able to delve into the more hidden regions of your disk.

You looking for things like:
a) a big difference between "free space" and "free +purgeable"
b) "hidden space" is large.
Both hidden space and free+purgeable have a right click drop down with more info (from DaisyDisk web site). This page https://daisydiskapp.com/guide/4/en/HiddenSpace/ and others in its sidebar.

For detailed insight and clearance run e.g. Omni’s DiskSweeper, Disk Inventroy X, or VizDisk

With respect, I don't think these three are capable of the deeper search required for understanding all of System Data. This is because they scan with user privileges only. But maybe, in this case, they might be enough.

 

[Buadhai]

My wife has an M3 MBA Running 26.1 with a 500 GB Internal SSD.

She was having trouble backing up and when I checked I was shocked to see that her System Data is just over 410 GB. (On my M2 MBA it is only about 48GB.)

I've searched around and find very little on what to do about pruning this down to a reasonable size.

I have emptied the trash which had zero effect. I ran Disk First Aid which found no errors and had no effect on the System Data size.

~/Library/Caches take up less than 2GB as does /Library/Caches.

Any ideas?

Update: It was suggested elsewhere that Onyx was useful in this situation.

I downloaded it and rain the Maintenance function twice. After that System Data had been reduced from over 400GB to just over 56GB. A much more reasonable amount.

 

[Buadhai]

Local Time Machine Snapshots? For detailed insight and clearance run e.g. Omni’s DiskSweeper, Disk Inventroy X, or VizDisk (all free, other programs are available 😁)

According to Onyx there were no local Time Machine Snapshots.

Is that with Time Machine? That can be both a cause or a symptom for large System Data.

In Disk Utility:
Select the system "data" volume labelled with a trailing " - Data".
In the menus, View > Show APFS Snapshots
You should now see an entry for up to 24 snapshots all created in the last 24 hours.
Right-click on one of the column headers and make sure "Private Size" and "Cumulative Size" are enabled.
Wait for it to fill out all the numbers.
Are any of the Private Sizes or the (cumulative) Sizes very large?

If these snapshots are all in the past 24 hours but a one or more is very big, just be patient as TM will remove the snapshots by tomorrow.

In Disk Utility there were also none.

If you need to scan the whole disk, use DaisyDisk (free trial, but you need the paid version) which allows you to scan "as Administrator" so that it is able to delve into the more hidden regions of your disk.

You looking for things like:
a) a big difference between "free space" and "free +purgeable"
b) "hidden space" is large.
Both hidden space and free+purgeable have a right click drop down with more info (from DaisyDisk web site). This page https://daisydiskapp.com/guide/4/en/HiddenSpace/ and others in its sidebar.


With respect, I don't think these three are capable of the deeper search required for understanding all of System Data. This is because they scan with user privileges only. But maybe, in this case, they might be enough.

See above. At this point, problem solved. I do appreciate your taking the time to offer a detailed explanation. I learned quite a bit and for that I am grateful. Now I know what to look for. Thanks.