Erasure codes are indeed a great illustration of the scale concept. If your designing to tolerate 2 simultaneous failures with 3 drives you need RAID-1 with N=3

Erasure codes are indeed a great illustration of the scale concept. If your designing to tolerate 2 simultaneous failures with 3 drives you need RAID-1 with N=3, 3x the cost of a single copy. If you have 15 drives you can do 12-of-15 erasure coding which is only 1.25x the cost of a single copy.