I recently set up a Seagate 2TB Expansion Hard Drive with my 2012 retina macbook pro, which is running El Capitan. When I try and organise files into folders on the hard drive, it seems to want to create a copy of the file, rather than just moving it into the folder. I have another Seagate hard drive which I bought a few years ago which behaves normally, and just lets me move files around without copying the whole thing. Does anyone know what could be the reason for this? I've tried to find a dedicated Seagate help forum but there doesn't seem to be one...!