So, I have an external hard drive with all my pictures. I want to use Photos to manage all this, keeping the Library file on this external drive, and without copying all the photos in the library (so I don't use twice as much space). If I look at this link: http://www.imore.com/how-use-external-and-referenced-libraries-photos-os-x It should be posible, and the option in preferences is pretty clear about this: BUT, when I start a new library after unchecking this "Copy to photos library" and add a few folders to Photos, the library grows to approximately the size of all these folders combined... How to avoid that? Is this a normal behaviour or a bug? Thanks!