I own a MBA mid 2013 128GB and every month its a struggle to manage space. HDD upgrades aren't possible for I'm considering moving my 75GB library to an external hard disk (HFS formatted) and opening it from the newly released Photos app. The ext hdd is usb 3.0. Will there be a performance hit? Will the moving be seamless? Presently I barely have 2 GB of space on my internal HDD. Thanks in advance for any help you are able to provide.