Tried to find similar posts but no one describes my problem fully, so... Brand new Mac Mini 2015 running Yosemite OS X Server. 256GB Flash disk It is running as a file server only and there are practically no apps installed. All files stored on LaCie Thunderbolt2 disk array Home folders: - nothing in the usually large folders (pictures, music, videos/movies etc) - no emails - no nothing, really 3 users accounts - with empty home directories OS X server gives message "Startup disk full" Tried a couple of graphical disk space usage apps and the amount of files shown does not even come close to 100GB. Have searched the disk for files to delete but can't find any... How do I solve this problem?