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I have a 2012 Mac mini running the latest Yosemite that I use as a server for file sharing, FileMaker, calibre, Time Machine and Plex. The Finder reports that the internal drive has a capacity of 499.25 GB with 48.03 GB available.

Listing the drive's contents with all folder sizes calculated looks like the following (having used defaults write com.apple.finder AppleShowAllFiles TRUE in the Terminal):

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Adding all that up brings me to a total of less than 350 GB. Running sudo du -sh .DocumentRevisions-V100/ reveals that that folder is only 17 M, contributing very little to the total.

So I seem to be missing about 100 GB of space. This isn't an emergency, I'm just trying to figure this out. Why am I seeing a discrepancy between the amount of space reported as available from the Finder and the amount of space I expect there to be given the size of the files and folders I see?

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If you don't have view permissions it will report itself as taking zero space to the directory that encloses it. This is especially visible with the "Users" folder. Take another User's folder.

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Notice how oddly small this folder appears. Yet it is reporting a valid file size, as I have read permissions to the folder.

Now look at the contents of this folder.

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Notice the variety of folder that I don't have view permissions for. As a result, when viewing the overall user folder, it simply assumes they take no space instead of reporting an error of some sort. Thus, the folder size is deceptively small.

If you want a more accurate report, I would recommend using something like DaisyDisk or a free alternative to scan the entire disk as admin so you can properly see what's taking up space.

  • Interesting idea, but I'm afraid that's not it. My first thought was that there are no other users, which is mostly correct. /Users/ has three folders, administrator, Guest, and Shared. In terminal I cded into Guest and used sudo to check the size contents. It's less than 9 MB. But I will try something like DaisyDisk to see if that sheds any light. – Chuck Jun 12 '16 at 23:58
  • @Chuck /Users/ isn't the only folder, I was just using it as an example since it's pretty obvious to see. – JMY1000 Jun 13 '16 at 0:19
  • Well, I've narrowed it down a little bit. It appears to be something in /Library. The Finder reports it as about 300 GB, but sudo find . -maxdepth 1 -type d -mindepth 1 -exec du -hs {} \; reports it as 384 GB, so it looks like at least most of the space is taken there. I'll keep investigating. – Chuck Jun 13 '16 at 0:47
  • @Chuck I would strongly recommend using a disk scanner, it will be much faster. – JMY1000 Jun 13 '16 at 0:50
  • Well, it looks like you were right. It turns out the missing data was found in /Library/Server/Caching/Data/, and the Finder couldn't see it for size calculation because of permissions. Honestly, I don't understand why, as ls -l reveals that the permissions for the "administrator" user are drwxr-x---, which I think means that the current user has full access, but at this point I don't care. Like I said, it wasn't an emergency, just curiosity, and since it's a cache, I can probably delete it without negative effect. – Chuck Jun 13 '16 at 3:13

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