Hi. I have an iMac and a MacbookPro and I'm looking at an external hard drive/s to keep backups of both and to store and edit my photographs in Lightroom. What kind of Ext HDD would you recommend in this case? Would you use the same one for the backups and pictures? Should I get a portable 2.5" one if I plan to travel? I would appreciate any advice on specific brands if possible. Thank you very much.