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?