Disk available space in Finder vs Manage Storage

Question

Disk available space in Finder vs Manage Storage

Hello!

I'm seeing a weird difference in how Mac OS (10.15.7 on a late 2013 15" MacBook Pro) reports the free space on the MacBook's hard drive.

The Finder info window reports the disk as having 84.51 GB of available space, but About this Mac > Storage reports 218.91 GB available (see screenshots below).

df in the terminal reports a third set of figures:

Nick@helios:~$ df -H
Filesystem     Size   Used  Avail Capacity
/dev/disk1s1   500G   408G    75G      85%

Any ideas what's going on here? Or suggestions for ways I could investigate this discrepancy? Which of these figures should I believe? Thanks for any assistance here.

Cheers,

N.

MacBook Pro 15″, macOS 10.15

Posted on Dec 2, 2020 7:07 AM

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Answer 1

Dec 2, 2020 7:43 AM in response to Wilddrums

Thanks for your response. Disk Utility at least has an internally consistent set of numbers: it reports 73.45 GB "free" but 217.78 GB "available", based on 144.33 GB of data being purgeable:

217.76 - 144.33 = 73.43 so the difference between "free" and "available" here does make sense (although, again, it's different from the Finder Info window which shows only 9.78 GB of purgeable data on the disk).

Why would these figures for purgeable storage be so wildly different? What's Disk Utility measuring that the Finder isn't? Apologies if these questions have been answered previously - I've not been able to find relevant posts searching the Forums, so if you have a link to share I would greatly appreciate it.

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Answer 2

Wilddrums

Level 5

4,274 points

Dec 2, 2020 7:30 AM in response to Nicholas Boalch

They are just not reporting about the same thing.

This was already discussed in the forums. I will not go in the details again. Just ask yourself: What is free space? For the user? For the applications? For the OS? For the File System?...

Use Disk Utility for more meaningful figures.

WD

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Answer 3

Wilddrums

Level 5

4,274 points

Dec 2, 2020 8:05 AM in response to Nicholas Boalch

Because Finder can only do its accounting on what the file system let it to see at a point in time. A very limited view.

Even "purgeable" means different things. As an example, it can include "deleted files not yet deleted" 😉.

With APFS you deal with "Volumes" in the same "Container" on a "Disk". Your screenshot shows only the volume data. On APFS free/available space is a volume statistic.

If I remember of a meaningful post on the subject, I'll post it back here.

Meanwhile, this is decades old knowledge. Nothing specific to Apple at all. You can find very detailed information on the Web: File systems, file allocation, storage allocation, computer resources management...

BTW no need to worry with all that stuff. Finder and Disk Utility are good enough. Unless you're a nerd like me...

WD

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Disk available space in Finder vs Manage Storage

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