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Disk Space Disappearing - Pleas Explain - Any Solution?

Q

qwerter18

macrumors member
Original poster
Feb 9, 2021
55
5
Hello again,

After setting up my new Macbook Pro 2021 M1 Pro - 14.1.2 Sonoma - I thought I could see my free disk space disappearing, but I could not make any sense of it.
Now I am sure, because I copied some files (40GB), started at 510 GB free memory.
I ended as expected at 470GB free disk space.
Then I deleted those files and free disk space was around 480GB now.
After working some time, I thought it would take some time for the free space to reappear...
But it wouldn't....it still was at 480GB.
After a reboot, the free disk space was only 420GB.
After a second rebbot, free disk space was at 417GB -> and decreasing... ending at around 416.38GB.
That is were it stayed.

I did some research but nothing helped.
I used Daisy Disk to see, that there was around 190GB of erasable stuff (including time machine snapshots 98GB)
Running a suggested script in terminl, deleting those snapshots, I ended at 608.47 GB of free disk space.

QUESTION:
Can someone please explain what is happening here?
I use an external SSD, once in a week, for time machine backups. When I connect, it starts automatically.
What are those snapshots used for? And why are they building up so fast.
Is there any way to stop this behavior? And to just do the SSD backup when I connect to it?

Best regards and thank you
 
qwerter18 said:
Hello again,

After setting up my new Macbook Pro 2021 M1 Pro - 14.1.2 Sonoma - I thought I could see my free disk space disappearing, but I could not make any sense of it.
Now I am sure, because I copied some files (40GB), started at 510 GB free memory.
I ended as expected at 470GB free disk space.
Then I deleted those files and free disk space was around 480GB now.
After working some time, I thought it would take some time for the free space to reappear...
But it wouldn't....it still was at 480GB.
After a reboot, the free disk space was only 420GB.
After a second rebbot, free disk space was at 417GB -> and decreasing... ending at around 416.38GB.
That is were it stayed.

I did some research but nothing helped.
I used Daisy Disk to see, that there was around 190GB of erasable stuff (including time machine snapshots 98GB)
Running a suggested script in terminl, deleting those snapshots, I ended at 608.47 GB of free disk space.

QUESTION:
Can someone please explain what is happening here?
I use an external SSD, once in a week, for time machine backups. When I connect, it starts automatically.
What are those snapshots used for? And why are they building up so fast.
Is there any way to stop this behavior? And to just do the SSD backup when I connect to it?

Best regards and thank you
Click to expand...

The snapshots are created by TM on the boot drive. They can be used to recover individual files or roll back the whole machine to an earlier state within last 24 hrs very quickly, without the TM backup drive being connected. (the rollback capability does not include rolling back to a previous macOS).

You cannot stop them happening if you have TM enabled. They are supposed not to show as used space in Finder but this does not always happen. The space is supposed to be given up when required, but this can be flaky too.

They are quite separate from what TM puts on the TM backup drive.

Best plan (IMHO) is not to fret too much about it. You will see free space come and go as the snapshots are only kept for 24 hrs. If you are in a bind for free space (as can happen during an OS update), you can delete them manually with Disk Utility or Daisy Disk, CCC, or Tinkertool System. In Disk Utility make sure "show APFS snapshots" is enabled in the view menu. Then right click the snapshots and delete.
 
Ah! Very helpful!
Thank you for your explaination! :)
I found APFS snapshots in Disk Utility and was wandering, what they are used for.
In "system settings" - "general" - "storage" - I just watched the "system data" grow from 60GB to 180GB...
And my free disk space is back to 480GB only.
Is that, where the snapshots would appear, in terms of disk allocation?
Because now there aren't any snapshots anymore... and right before my eyes I could see those 120GB disappear again?!

I could live (would live) with the snapshots being the storage eater, but now I don't know if this was the problem in the first place...
 
it is getting better and better... or worse...

I had about 60GB of free storage (without any problems), when I started deleting unneeded files.
I was back at about 130GB of free storage.

After a couple of weeks I was back at 85GB only... but now my MAC tells me, it has no more free diskspace.
Finder says, I have 85GB free.
I restarted my MAC and still 85GB of free space in finder, but no more copying or other tasks possible, as the warning appeears "No more free disk space"
 
MacOS doesn't delete files immediately, instead moves them to the "Trash", where you have a chance to recover accidentally deleted files.

In storage settings, I can see I have 30GB in trash, and that trash is not set to automatically delete files that have sat there for a while... apparently I have to turn that on manually, which I've now done.

To remove all the trashed files immediately, open Finder or click on the Desktop. Choose 'Finder' on the menu bar, and "Empty Trash...", or while in the storage settings, click on the Trash line, then click the empty trash item at the top, or manually pick a set of bulky items to remove, and click delete.

Also note, SSDs require a certain amount of free space to operate effectively, and having a drive nearly full will severely impact system performance. This may be why it's refusing to fill the last 60-80GB, or perhaps that's the size of your trash. I honestly don't know. You're in a perfect spot to compare the size of your trash to that reported but unusable free space.
 
Thank you for your detailed answer.
Still, I am unhappy with the use of disk space allocation apple uses, and making me pay for it.

I checked trash. Nothing in it.
I checked snapshots. Only one snapshot: 150GB of use. (despite I was doing a time machine backup just before)
Deleted the snapshot. Back to 320GB of free disk space. WTF

What I don't get, not letting me rename files or just move files, with 85GB left.... Sucks.
Telling me, free space will be available if I need it, isn't true, apparently.

While there obviously is 320 minus 85 minus 150 = 85GB!!!
Another 85GB left free somewhere (not being freed for me, when I needed it)

The ideas of apple are OK, but the way it is not working is not OK, and needs improvement. In my opinion...
☺️
 
OP:

Do you use time machine for backups?

If so, have you tried deleting the snapshots tm makes?
(this can be done using disk utility)
 
Mac system space management is a black box which has prompted innumerable posts. There are a number of system files that can take up space, such as caches, snapshots, etc. They are constantly changing. Trying to keep on top of it is a losing battle. A program such as Daisydisk can give you some insights.

Your best bet if your boot disk is getting low on space is to get a very large external boot disk so you don't have to worry about it.

Be sure to keep 20-30% free space on all of your drives.
 
@Fishrrman
Yes I do. And yes I did that. Freeing 150GB.
But of course, after one day it is in use again.
Now, there is 200GB free and 150GB Snapshot.
So a total of 350GB 😂😂😂

@HDFan
Yes. Feels good, not to be the only one with those problems. But also feels wrong, that it has to be like this.

Thanks guys/girls for your help.
I just baught a 2 TB SSD... 😂 🤷
 
OP:

Advice I repeat often in this forum:
You might consider dropping time machine, and replacing it with either CarbonCopyCloner or SuperDuper.

CCC gives you the option to either keep snapshots, or turn them "off".
I turned them OFF -- don't need them.
 
That might have been the advise I needed.
Thank you 👍
Do you know if I can (with CCC)
Backup my Macbook, and clone it to another Mac?
 
Fishrrman said:
You might consider dropping time machine, and replacing it with either CarbonCopyCloner or SuperDuper.
Click to expand...

Although I keep posting to not rely on TM it has a big advantage over CCC or SuperDuper. It supports versioning so you have all versions of a file back to the time that the original TM backup was made. I can restore any version of my TM files created on or after October 2023.
 
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HDFan said:
Although I keep posting to not rely on TM it has a big advantage over CCC or SuperDuper. It supports versioning so you have all versions of a file back to the time that the original TM backup was made. I can restore any version of my TM files created on or after October 2023.
Click to expand...
You mean by 'versioning' storing one (or none) version per backup run?
That is done by CCC in 2 ways:
1) snapshots, that may contain a version,
2) 'safetynet' that collects modified files per run by date+time.
For details: https://bombich.com
;JOOP!
 
HD wrote:
"TM it has a big advantage over CCC or SuperDuper. It supports versioning so you have all versions of a file back to the time that the original TM backup was made."

I believe the LATEST version of CCC (now up to "7"?) has added features to allow it to "mimic" tm in this regard. Not sure, haven't used it. I'm not interested in "versioning", anyway....
 
It's why I keep using TM. Just for this purposes. Saved my behind many times when I worked and needed to go back and retrieved a version even if its been a few years.
 
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