No, not the PBS Show from the 80s.
If you want to verify there’s safe and secure copies of your work/files, this rule is the easiest, best method, and cost effective.
3 back ups on your pc
2 copies on different external devices (flash drives, dvd-r, or external hdd usually)
1 copy off site (Dropbox, or some other server)
While on paper this may seem like a lot of wasted space, time, and resources, if you’re working on something important this will ensure there’s always a plan B somewhere.