Because I wanted to back up an external that holds my immediate backups, I bought up on the Carbonite subscriber schedule. It now backs up my hard drive and ONE external (I actually have three, so I have named one of the drives Carbonite so I rermember which one to put the GOOD stuff on for backup). Then Carbonite began to nag me, because an option of my bought-up subscription is a mirror image for which I need to commit one external (nothing else can be here) of at least the same size as my hard drive, and Carbonite will handle the software mirror backup to my external drive. I tired of the nagging and finally moved files from the one drive to the drive that will be backed up to the Carbonite servers and let Carbonite set up the mirror image. It is doing that now, almost 23% done, and I can use (though it is sluggish) my computer while the image is being made. I suspect I will one day be happy to have an up to date image and backup. If you are considering a backup system, you might want to consider what is now available at Carbonite since these options are relatively new there. Elaine