iMac M4 SSD storage significantly reduced after Golden Gate upgrade

fleetwood77 wrote:

I have exactly the same problem on a 2024 Mac mini. My free space has reduced by 130gb. I called Apple Support yesterday, they talked me through deleting a number of files and restarting but this had no effect so I rang them back. I've been asked to wait until tomorrow (Thursday) and if nothing has changed to contact them again and they may refer me to the engineering team. 2 days in and nothing has changed - I have only 220Gb free rather than 351Gb - interestingly when I look at my storage details its shows 351Gb available with only 220Gb free - my system data is now 140Gb so there is clearly something going on.

Your figures warrant further investigation by Apple. You currently see approximately 351 GB available, 220 GB free, and 140 GB classified as System Data. 

Apple notes that available storage can include both free and purgeable space. Apple Support — Free up storage space on Mac

Since Apple Support has already had you delete files and restart the Mac without changing the situation after two days, I would now gather diagnostic information rather than continue deleting files.

First, make sure you have a current backup. 

Then open Disk Utility, select View > Show All Devices, and record the capacity, used, and available/free space for the internal physical disk, APFS container, Macintosh HD, and Macintosh HD - Data. 

This provides filesystem-level information that is useful when investigating a difference between the storage figures shown in macOS. Apple Support — Disk Utility User Guide for macOS 27

Next, select View > Show APFS Snapshots and record whether any snapshots are present and the sizes reported for them. 

If you use Time Machine, tell Apple Support, since Time Machine can create local snapshots. Apple Support — About Time Machine local snapshots

I would also run EtreCheck from your original user account and save the report. This may provide additional diagnostic information if Apple escalates the case to Engineering.

First Aid can be considered if Disk Utility reports a problem or if Apple Support specifically recommends running it. 

If you do run it, follow Apple's procedure and ensure you have a current backup first. Apple Support — Repair a storage device in Disk Utility

When you contact Apple again, provide the original and current storage figures, explain that the recommended deletion and restart did not change them, and provide the Disk Utility, APFS snapshot, and EtreCheck information.

The 140 GB System Data figure should not by itself be treated as an explanation for the approximately 131 GB difference between the 351 GB available and 220 GB free figures. 

The Disk Utility and APFS information should first establish how the storage is actually being reported.

gsyrba wrote:

Available does not mean used.

It does. Otherwise it would be "free".

It means free space that is available to be used.

Technically speaking, it's used space that is available to be freed, should the operating system (not you) decide that it's necessary. To date, after several years, I have not seen a single instance where "available" storage was actually available when the user needed it. Regardless of the amount of storage "available", when free space is too low, the system refuses to proceed. Most people never notice this until they try to download some huge OS update that typically requires 15-30 GB free. At best, it takes 1-2 days after storage is exhausted before the operating system will grudgingly give up some of that "available" storage. Then the entire process repeats next month at the next OS update.

If that 212GB of "available" space was used, as well as the space that actually already is used, the hard drive would be 100% full.

In most cases, when people run into this kind of storage problem, the drive usually is 100% full.

In your case, you've reported "available" values of 198, 58, 115, and 43 GB. That's more than the typical variability. I recommend people keep 100 GB of free storage. That's what I do and everything runs fine. You may be able to get away with 50 GB free, but performance will get noticeably worse as the operating system starts to spend more and more of its time trying to keep this "available" storage free to keep the OS running.

gsyrba wrote:

Available does not mean used. It means free space that is available to be used.

I can confirm @etresoft is absolutely correct from my own personal experience. macOS will not release the "Available" storage even when the system requires it. With macOS and the APFS file system "Available" is not synonymous with Free. In fact the Free storage space value is the only accurate storage value in macOS.....even the "Used" value can be misleading with certain configurations. The only place where the Free space value is correctly shown is in Disk Utility. Yes, that implies macOS shows an incorrect Free space value in another location.

If that 212GB of "available" space was used, as well as the space that actually already is used, the hard drive would be 100% full.

That is exactly what @etresoft is saying.

Your system may be nearly out of actual Free storage space....we have no way of knowing for sure because you've only posted "Available" storage values. Sometimes the "Available" space will be the same (or nearly the same) as the actual Free space.

When the Free space completely runs out, then bad things will happen. In fact, once the APFS volume has no more Free space, then it will be impossible to move or delete anything to make more room due to how the APFS file system works which means to get the system working again requires erasing the system & restoring from a backup.

Even a 100GB of Free space can sometimes disappear very quickly with seemingly simple tasks.

By way of update I decided to erase all content and settings and set up my Mac mini as a new machine. I followed the Apple instructions to erase all content and settings under transfer or reset under system settings. I didn't use recovery to download a new copy of MacOS27. I use iCloud for my data and my photographs and photos are on external drives. This seems (so far) to have resolved my issue with free space, and before I reinstall my apps I currently have 418Gb out of 494Gb free and my system data is showing a more usual 38 Gb rather than the 130Gb it was reporting before I reset everything today. This also seems tomhave resolved the issues I was having with my magic mouse not working properly (this is the subject of a separate thread I read yesterday. Hopefully this has now resolved otherwise I will get back in touch with Apple Support

Since you are still experiencing the anomaly after a few days consider downloading and running EtreCheck.

Instructions: How to run the Etrecheck Diagnostic Tool - Apple Community

Following those instructions, post its report in a reply to this Discussion so that others may review it and provide suggestions.

Apple Support is not interested in EtreCheck, besides, they will be reluctant to suggest certain actions that might reflect poorly on developers of certain notorious products that could be to blame.

EtreCheck may provide actionable information, or it may not, but I would also be reluctant to erase the Mac and set it up again, lacking a justifiable reason. That extreme step may yet be required, but unless you identify the underlying cause "the same bloat will happen again" as you suspect.

Same happened to me - about 100GB lower availability. But 24 hours later the Mac released it. Back to normal now.

gsyrba wrote:

I guess what baffles me the most is that if you look at the storage legend

I will not look at that display.

the system data alone is taking up roughly 1/3 of a 512GB drive.

It's not system data.

Are you sensing a trend here? "available" storage is used. "available" storage isn't available for use. So why would you think that "system" data has anything whatsoever to do with the system?

Years ago, when people encountered unusually high values for "system" data, it was usually local snapshots from Time Machine or some 3rd party backup tool. Those are still possible. But for the past few years, there are so many other possible causes that it could be virtually anything.

The only way to track this down will be with a 3rd party storage management tool that tells you exactly how large various folders are. Then, when you find the folder that's way too large, you can track down what's causing it.

A simple restart reduced my systen files from 70GB to 54GB

The Finder needs a day or so to reconcile and eventually release free space.

I have exactly the same problem on a 2024 Mac mini. My free space has reduced by 130gb. I called Apple Support yesterday, they talked me through deleting a number of files and restarting but this had no effect so I rang them back. I've been asked to wait until tomorrow (Thursday) and if nothing has changed to contact them again and they may refer me to the engineering team. 2 days in and nothing has changed - I have only 220Gb free rather than 351Gb - interestingly when I look at my storage details its shows 351Gb available with only 220Gb free - my system data is now 140Gb so there is clearly something going on.

I sure hope you are right. All I did yesterday on the computer was copy some photos for a business client from the iMac to my iPad. Nothing else. Today I am down to 44GB of free space. So it seems to be increasing, not decreasing.

Thanks for the help so far, an update - after spending some time speaking with different Apple Techs my situation hasn't changed and I still have system data of 120Gb rather than the 20-40Gb it should be, with my free storage still showing 100Gb less than before updating to MacOS 27. After trying a number of different things with the techs I am now going to do a clean install of MacOS 27 which should reset everything. I am also going to reinstall all my apps anew rather than restore from Time Machine. Hopefully this will sort out this problem. I won't be able to do this until next week but will update once I have completed it.

Please update us on this thread so I will see it. I'm really curious if that will be my best option as well. I haven't been using my Mac the past 24 hours... just my iPad instead. I logged onto the iMac an hour ago just to see if it went down like others have said on this thread. It's actually bloating more. I started two days ago with 58GB free, then yesterday it mysteriously went to 44GB free, today it's at 43GB.

I can't even imagine doing a clean install considering how many documents and other things I have. They are all backed up in Time Machine of course, but that sounds like a bad choice to use since it will probably return me to just before the update to Golden Gate... then I feel the same bloat will happen again. Besides, manually going through every app to individually back up 15 years of files elsewhere long enough to do a clean install sounds a bit overwhelming.

Thank you, John. I'm going to give it one more day. Since midday today it decreased a fair amount. I now have 115GB of free space. But since I started with 198GB right before updating that still seems excessive that Golden Gate would take 83GB of space. If it drops to a reasonable amount tomorrow I'll call it good. If not, I'll run the Etrecheck tool, and post the results here. Thanks again!

Sounds good. In case it's relevant you wrote that you had not been using the Mac for 24 hours or so. Although it's not necessary to constantly interact with a Mac for the Finder to reconcile free space, the Mac has to at least be "on" as in not shut down for that to happen. In any case I suspect it will eventually settle down to normal.

I do leave it on but locked when not in use... other than once per week doing a shutdown for a few minutes, then a restart. Our IT team at work used to stress that we do that, so that carried over to my home computer as well many years ago.

Odd thing I noticed this morning... If I go to System Settings > General > About, then I see 212GB free space, as you see in the first screen shot. But if I go to System Settings > General > Settings, then I see 86GB less free space, as you see in the second screen shot.

gsyrba wrote:

Odd thing I noticed this morning... If I go to System Settings > General > About, then I see 212GB free space

Do you? I see 212 GB of "available" space. Do you want to know another word for "available"? "Used". AKA "Not available".

But if I go to System Settings > General > Settings, then I see 86GB less free space, as you see in the second screen shot.

I'm skeptical about that too. If you hover your mouse over it, it says "available". So is this yet another "available" fantasy or is it actually free space?

Available does not mean used. It means free space that is available to be used. If that 212GB of "available" space was used, as well as the space that actually already is used, the hard drive would be 100% full.

HWTech wrote:

even the "Used" value can be misleading with certain configurations.

Any file has the potential to share one or more blocks with another file. And some files may be sparse, effectively making it have two different sizes, both valid in different contexts. Other files are too small, and consume an entire block of storage. And still more files could have additional metadata.

The only accurate values are calculated from low-level block storage.

In fact, once the APFS volume has no more Free space, then it will be impossible to move or delete anything to make more room due to how the APFS file system works which means to get the system working again requires erasing the system & restoring from a backup.

But if free space is too low, it may be impossible to restore from backup. The user runs out of storage, even burning through "available" space. Maybe they even try to delete those pesky "cache" files, although this is not even required.

So they give up, erase the drive, and reinstall the operating system. Only this time, the current OS version is maybe slightly different. Or maybe it has some of those cache files that were deleted before. Since the drive is practically empty after a reinstall, there's no need to purge any storage like before.

But now, the backup is too large to fit into the available space. I've never seen this happen, but it seems like a logical possibility to me.

Even a 100GB of Free space can sometimes disappear very quickly with seemingly simple tasks.

I once lost 300 GB in a few minutes when Xcode went nuts for a while. I was able to hack it in Recovery Mode. After an update, I was able to remove my hack.

You both make good points, and yes, I have always tried (and succeeded on my last two iMacs with 512GB hard drives) to keep 100GB free - up until this update. That's why I'm concerned that updating from the most recent release of Tahoe, to Golden Gate, is chewing up 83GB of hard drive space. That seems incredibly large just for the OS. And yes, Disk Utility shows the same.

I guess what baffles me the most is that if you look at the storage legend (which I will attach again) is that the system data alone is taking up roughly 1/3 of a 512GB drive. Up until last week when I would look at that, the system data looked like it took up less than half of what it does now.

A simple restart is what I did before making the original post. That was followed by a shutdown for a few minutes, and then restarting again. It didn't change a thing, hence my reason for the post. It's been 10 days now, and it still shows that this update alone has used a total of 83GB of space.

What did you do to help reduce it? What I mean is any steps to force the Mac to react?

Just waited.

I have done this process several times which is the only way I have found to reduce the system storage count.