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What is going on with MacOS Free Disk Space Remaining in Sequoia?

smirking

smirking

macrumors 601
Original poster
Aug 31, 2003
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Silicon Valley
Is anyone else noticing that their disk space utilization numbers in MacOS Sequoia have completely separated from any relationship with reason or reality?

Today, I just made a bunch of serious filesystem changes that should have freed up 200GB and Sequoia reports... "here's the 10GB you just saved you virtuous boy!" The odd thing is that Omni Disk Sweeper, which I use to get a better real time look at my space usage has also stopped being dependable. It gives me the same overview numbers as MacOS does now (but the drill down directory summaries are still dependable).

I know I have more disk space than is being reported so I'm not worried about actually running out of space in the near term. I just don't want this to continue and unexpectedly run out of disk space 6 months from now because I stopped trusting anything MacOS tells me.
 
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As I understand it, deleted files are marked as "purgeable" but aren't actually deleted until the "purger" runs, which I believe is on a schedule. The space might free itself at some future point.

The other trick is to delete Time Machine snapshots. I usually do this with tmutil but I believe it can be done through Disk Utility too.
 
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Nermal said:
The other trick is to delete Time Machine snapshots. I usually do this with tmutil but I believe it can be done through Disk Utility too.
Click to expand...

Don't those usually delete after you make a Time Machine backup? Normally I get a pretty good idea of what my real disk space is after I do a Time Machine backup and the local changes log gets flushed, but that's no longer true. Nothing changes after I run Time Machine and it's already been several days since I pruned my filesystem without any change.

Ugh.
 
smirking said:
Don't those usually delete after you make a Time Machine backup?
Click to expand...
You'd think so, but I often find hourly backups going back maybe 48 hours despite TM backing up every hour. I think it keeps local copies so that you can restore recent mistakes quickly (which probably doesn't happen that often: it reminds me of on Windows where the scanner drivers install an app into Startup because you obviously want to do nothing but scan things all day).
 
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Nermal said:
You'd think so, but I often find hourly backups going back maybe 48 hours despite TM backing up every hour. I think it keeps local copies so that you can restore recent mistakes quickly (which probably doesn't happen that often: it reminds me of on Windows where the scanner drivers install an app into Startup because you obviously want to do nothing but scan things all day).
Click to expand...

Hmmm... it looks like they're only supposed to be kept around for 24 hours:

About Time Machine local snapshots on Mac

Time Machine makes copies, each hour, of files that have changed on your Mac.
support.apple.com

Normally, I see the local snapshots in my /Volumes folder, but I see nothing this time.
 
smirking said:
Hmmm... it looks like they're only supposed to be kept around for 24 hours:
Click to expand...
Ah, yeah, it'll be 24. I was thinking "yesterday plus today", but of course if it's midday now then that'd be 12 hours yesterday and then 12 hours this morning.

smirking said:
Normally, I see the local snapshots in my /Volumes folder, but I see nothing this time.
Click to expand...
Does "tmutil listlocalsnapshots /" show anything?
 
Nermal said:
Does "tmutil listlocalsnapshots /" show anything?
Click to expand...

Yes it does! It shows about 2 days worth of backups but also after I ran that, the backups showed up in my /Volumes folder... though I also started a new Time Machine backup run so I don't know if that command or me starting a new backup made the local snapshots visible to Finder.

Let's see if those local snapshots get cleared after I finish this latest backup run.
 
OK, I completed another time machine backup and still nothing changed. When I ran tmutil listlocalsnapshots, I continued to see the snapshots, plus a couple of mysterious snapshots that were named differently. I was able to delete the regular snapshots by running tmutil deletelocalsnapshots, but those two odd ones couldn't be targeted.

They looked like this:
com.apple.asr.22854
com.apple.asr.7263

Someone suggested running this to clean them up:
tmutil thinlocalsnapshots / 999999999999999 4

That worked and those two snapshots which have probably been stuck there for quite some time were eating up 400GB!

I now have almost 500GB in free disk space!
 
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Nermal said:
The other trick is to delete Time Machine snapshots. I usually do this with tmutil but I believe it can be done through Disk Utility too.
Click to expand...
Yes in Disk Utility Menubar > View > Show APFS snapshots

You can select individual or all snapshots and delete them with the little minus sign bottom left.

I always have 24 or 25 local TM snapshots even though I also have TM connected and running. So it is not the situation that they are deleted next time TM drive is connected and run.

I only find it worth bothering deleting them when I have just deleted huge amount of data and have. need of the free space.

I have found these local TM snapshots extremely useful sometimes for very rapid rollback to an earlier state. Much quicker than erase/migrate from standard TM backup on an external, (but can't rollback across and OS update since Big Sur). Of course TM created local snapshots only go back 24 hours but CCC has much more flexible local snapshot retention policies, and also enables deletion.
 
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Mike Boreham said:
I only find it worth bothering deleting them when I have just deleted huge amount of data and have. need of the free space.
Click to expand...

I normally don't bother either, but something had been off for some time and I've been using my dev tools for doing disk hungry things so I couldn't afford to not know how much space I really had. It turns out I had quite a lot of space.

I think the weird looking snapshots that were eating up 400GB must have been related to a couple of Time Machine runs that went wrong and I did have exactly two backups that aborted due to unspecified problems.
 
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OK, after all that, Disk Utility reports 467GB Free. System Report is showing 550GB free, which might be the first time that System Report is telling me I have more space than everything else.

It doesn't really matter right now, but wow what a mess this is.
 
From here it looks like this - if Apple Intelligence is enabled, then amount of purgeable data and storage use data does look realistic and "Storage" calculation in Systen settings is able to complete. If Apple Intelligence is disabled, "Storage" calculation is unable to complete System Data calculation and amount of purgeable data is bigger by that same amount, which is marked as System data when Apple Intelligence is enabled.

Apple Intelligence icon has BETA on it and it looks like this beta feature has made beta-testers of us all no matter if it is enabled or disabled.

P. S. There's no local TM snapshots on any volumes...
 
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