I am using iCloud photo library and have chosen to download originals to my MacBook Pro because I want to have local copies of all my photos. My SSD is almost full and I will most likely have to switch to optimising mac storage and storing originals only in iCloud. I would like to be able to still easily back up the whole library to an external drive. Is there any reasonable way to accomplish this for a 300GB library? I have a 1Gbps internet connection in my home so there's enough bandwidth. I don't want to have an external drive as my primary library location since I wouldn't be able to use photos without the drive attached. I assume that I'm not the only one with MacBook Pro and big photo library so I'd also like to hear about any alternative solutions that offer easy backups and ability to access the photos with all iOS devices.