I was using rsync to backup unix / linux directories to a mounted cifs share. (This is a samba share mounted under Linux). The server is Ubuntu. Problem I had was rsync kept copying the same files over again even though they did not change. The solution was to add –modify-window=2 This adds a 2 second window to the rsync compare. Fat file systems write timestamps weird and this corrects for the problem. I also needed to modify the rsync command and change it from rsync -a to rsync -rltDv fat also does not keep owner or group permissions. A big thanks to my friend, I’ll call him T for helping me figure this one out!