Where is my missing drive space? 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):



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?
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.



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.



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.