"About my Mac" and "Disk Utility" show vastly different disk storage

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Level 1

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"About my Mac" and "Disk Utility" show vastly different disk storage

I borrowed a friends new MacBook (Retina 12 inch 2017) with 500gb flash storage running High Sierra10.13.2. Now I want to return it, I have deleted all the many large image and movie files I created (moving them to the trash and emptying it) and have been through all the steps here: How to free up storage space on your Mac - Apple Support

... as well as restarting it multiple times, waiting for it to resolve itself overnight (I know!) and, more rationally, running "First Aid" on the HD via Disk Utility. No problems show up and nothing changes. The variation remains massive.

I still have the following conflicting information:

About My Mac > Storage tells me verbally I have 341.99GB of 499GB free (whilst showing a very different picture visually - see below - that doesn't look like 2/3 free to me) whilst Disk Utility shows that I have 52.64GB free (its graphic and About My Mac's look like they agree - but the bulk of the files are now showing as "system"). Screen shot below.

System Information also shows the disk to be that full (screen shot also below) I have deleted enough large files to know that the figure in About My Mac > Storage is almost certainly the correct one.

I don't want to hand this machine back to its owner in this state, nor do I want to have to wipe everything and restore the machine from a Time Machine backup. So what is going on here? Is there a solution? How can I get Disk Utility and About My Mac to give me accurate information about the state of this MacBook so I can give it back to its owner in a good state?

Thanks in advance.

This is a screenshot of About My Mac > Storage and Disk Utility on the same disk:

MacBook, macOS High Sierra (10.13.2)

Posted on Jan 18, 2018 5:28 AM

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Answer 1

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John Galt

Level 10

141,024 points

Jan 19, 2018 5:18 PM in response to Mary London

You described it just fine and I understand. The "Storage" graphic will include temporary files created by the system and totally inaccessible to the user. They are not included in the Finder's calculations, including sizes and capacities reported by Get Info.

Those temporary files are supposed to be truncated when the system needs more space. That's happening as expected on all my Macs, but there are reports on this site indicating it's not happening in some cases. I don't know why that would be, but I have my suspicions.

The manifestations of APFS will result in some apparently bizarre calculations, such as this excerpt from another Discussion (the subject of which is otherwise unrelated):

John Galt wrote:

...

Here is one illustration of the problems you can encounter when attempting to correlate Finder reported space vs. apparently unallocated capacity:

Notice the capacity of that Mac's flash storage (256 GB), the apparent amount of stuff in the Trash (nearly ten times that much) and the available space as reported by Storage (62 GB).

After emptying the Trash:

After a Time Machine backup, which I had intentionally put off for a few days after your last reply:

...

Notice that Mac's storage device capacity (250 GB) and the amount of stuff it contains (well over 2 TB in the Trash alone). Yes, I actually created 2.26 TB of random stuff on that Mac, which I then dragged to the Trash. I could just as easily have dragged it out again. Get Info for that Mac's flash storage would have reported on the order of 2.4 TB used on a device whose capacity is a tenth that size (unfortunately I didn't take a screenshot of it... and I don't want to repeat that exercise. It took long enough to generate 2+ TB of random data).

Moral of the story: don't worry about returning that Mac in the condition it's in. It's working the way it's supposed to work. However, if I were you, I'd restore a Time Machine backup corresponding to the time you took possession of it, lest your friend have the same questions you do.

Should I contact Apple Support and let them know about this?

Be my guest. I have not been able to get them to explain it any better than I just did though. Perhaps one day Apple will publish a Support document explaining things in greater detail. I think it's far more likely that they will simply deprecate the Finder in some future macOS upgrade though, leaving file management to the apps that create them, just as iOS has always done. iPhone / iPad users don't seem to care about that subject a bit. Ignorance is bliss.

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Answer 2

Mary London Author

Level 1

43 points

Jan 18, 2018 8:30 AM in response to Csound1

Thanks very much for this speedy reply.

I have tried re-indexing Spotlight several times now, following the instructions in this article carefully: How to rebuild the Spotlight index on your Mac - Apple Support

However it will not rebuild it - I add and then remove Macintosh HD as instructed (clicking OK as I have the relevant permissions) and absolutely nothing happens. I've tried this process on my own MacBook Pro (Retina 15 inch mid 2014) also running High Sierra 10.13.2 and it doesn't work there either. Am I doing something wrong?

You may be right about Disk Utility being correct about the disk storage in this case, but I have deleted about 350GB of data already, and there is nothing else left for me to delete on that MacBook now beyond a handful of apps which I want to keep on there.

When I follow the instructions about Managing my storage from About My Mac > Storage there's nothing left to do - I've already deleted files that held over 280GB of data, and completed "Optimise Storage" When I "review" files there are no large files left to delete. When I look at the Downloads tab, and try and delete a .pdf (the only remaining file of 2mb) in "reduce clutter" I get the following message:

This is what now shows in About My Mac > Storage > Manage showing where the data is on Macintosh HD:

.... with a mystery "greyed out" System value of 381.88 GB that I can't touch. I'm completely perplexed! How have all those deleted files of mine ended up as untouchable system files I can't remove?

Is there another way to re-index Spotlight? And why is the majority of the storage on Macintosh HD now labelled "System" and untouchable? I'm sorry, but this makes no sense to me!

Thanks again for your help.

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Answer 3

Mary London Author

Level 1

43 points

Jan 25, 2018 3:28 AM in response to John Galt

As a postscript, I thought I'd let you know that finally both About my Mac and Disk Utility agree, the hard drive is as it should be, and that all the items I had put in the trash no longer show up in either:

Yay!

However I have no way of knowing how this happened!

But in case anyone else has this problem, the things that I did were:

1. A Time Machine backup of the MacBook in its current (strange at the time) state. Looking at John's reply above, I think that this might be well worth doing if you are having the same problem, and could even have fixed it completely. Perhaps the system stores the deleted files until it's certain that everything has been backed up safely.....?

2. I ran Etrecheck on the MacBook, having used it on my own MacBook Pro for something else and found it very helpful. This also reassured me that everything was working properly (and was properly backed up on a Time Machine) when I returned this MacBook to its rightful owner.

I came across Etrecheck on other Apple Support pages because of a completely different issue, and have always found it very useful. It is discussed here: Is Etrecheck a safe app?

I'm not sure I'm at a high enough level to start recommending it on here, but I will put a link below as it's a free tool that seems to avoid the issues that other 3rd party apps I've previously used on my Mac seem to fit as standard!

Thanks again for all the help here. Really appreciated.

https://etrecheck.com/

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Answer 4

Csound1

Level 9

59,973 points

Jan 18, 2018 11:12 AM in response to Mary London

Judging by previous experience, Disk Utility is correct, that other thing is not. Re-indexing Spotlight may resolve it. To re-index spotlight follow these directions.

How to rebuild the Spotlight index on your Mac - Apple Support

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Answer 5

John Galt

Level 10

141,024 points

Jan 19, 2018 11:01 AM in response to Mary London

Did your friend not create his or her own Time Machine backup prior to lending that Mac to you, or did you not create one when you received it?

It seems to me restoring from either appropriate backup that would be the obvious solution.

About This Mac's Storage display calculates disk usage differently than any other method, because it includes storage that lies beyond the user's ability to manage or control. There will always be a discrepancy between the two.

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Answer 6

Mary London Author

Level 1

43 points

Jan 19, 2018 11:03 AM in response to John Galt

Thank you for this. Yes indeed, happily I have all the Time Machine backups I need to restore the machine to its earlier state, and I now understand why there might be a discrepancy between the two ways of calculating disk usage - although it has to be said that the "discrepancy" is well over half of the hard drive's total capacity!

However, and perhaps this is my poor wording of the question, I find it alarming that the files that I have moved to the trash (about 300GB of image files - RAW, Photoshop .psds as well as .jpgs) and then deleted "permanently" by emptying the trash, now turn up as system files that I can't touch, let alone clear out. (The screen shot is above, showing 331.88GB as greyed out system files)

I really appreciate your help with this, however as this is almost a brand new machine (it's less than 4 months old), and as it's fully updated to the latest iteration of OSX (and always has been) I'm finding it hard to accept that it's normal that I have to restore a Time Machine backup in order simply to delete files and create space on the MacBook's hard drive?

I can and will try to resolve the pressing issue with Time Machine backups, but what's to stop this from happening again? Is it ever going to be possible to delete anything on this MacBook? Should I contact Apple Support and let them know about this?

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Answer 7

John Galt

Level 10

141,024 points

Jan 25, 2018 4:14 PM in response to Mary London

Great! Thanks for the update.

Perhaps the system stores the deleted files until it's certain that everything has been backed up safely.....?

That's pretty much how it works. Your experience closely mirrors mine. After doing some work you will find that System will fill up again. That's normal and should not be a concern (but read my earlier comments).

"Safe" is subjective and connotes many different concepts. EtreCheck is perfectly "safe" with common-sense caveats: obtain it from a source authorized by its developer, use it in accordance with its intended purposes, and recognize its limitations. Of course the same can be said of anything (even Mac malware!), but running it does not modify a Mac in any way, it does not require an installation procedure, and removing it is accomplished by simply dragging its icon to the Trash. That's only a few of the criteria I consider "safe". You can certainly recommend it.

Nothing is free though. The costs of maintaining and hosting it are borne by its author. That might not be possible forever.

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Answer 8

Mary London Author

Level 1

43 points

Jan 25, 2018 11:14 PM in response to John Galt

Thanks so much, John. That’s great and very reassuring to know. What a great common sense approach too! Re Etrecheck, I’ve donated a small amount to the developer to help keep it going and always download from Etrecheck’s own website. These things are worth supporting! Thanks again.

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Answer 9

Mary London Author

Level 1

43 points

Jan 20, 2018 3:24 AM in response to John Galt

That's fantastic, John, thank you. I will restore it to the relevant Time Machine back up and try to explain this to the MacBook's owner! Or maybe not.... Ignorance is bliss 😉

Thanks again.

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