Shortly after I bought my 512 GB rMBP I purchased an external SSD, Samsung's T1 in the 1 TB capacity, and it works very nicely to stash everything that I don't need on a daily basis but still need to access from time to time: photos, documents, non-iTunes movies, etc., etc. I plug in the external SSD when I need something and it is very fast and responsive. When I'm done, I simply unplug and put away the device, although of course it is possible to keep it plugged in all the time as well, and some people do just that. Now Samsung has just newly released a 2 TB SSD, the T3, and at some point I'll probably be purchasing one of those as well to use either as an additional supplementary drive or as a backup drive. I also use other (non-SSD) external drives specifically for backup, too, of course.