I have used usb keys to store folders of files containing only text files thinking they were a huge step forward from having to burn compact discs. But one by one when I have tried to access those files to update them, I receive an error "this disc is unusable". I had multiple backups but it got really messy trying to maintain all of them. Now, I back up onto an external HDD and when necessary go to it for extraction. I have found 4-8 gig usb keys are handy if you don't put too much on them.