Hi all, I have a little question regarding time machine (and yes, I am new to Mac). I noticed that every hour, it does its back-up on my external 1TB drive but... ...when nothing has changed (and I mean nothing as I was not using it), it still backs-up about 15GB of files. Why is that? Isn't it a differential back-up based on filesystem that would just copy the new/updated files? Thank you for your answers.