One of the reasons they say "RAID is not backup" is because the kinds of things that take out a single drive, take out multiple drives together often enough tha

One of the reasons they say "RAID is not backup" is because the kinds of things that take out a single drive, take out multiple drives together often enough that it surprises people. I've seen more than one person report that they had a RAID NAS at home, thinking their data was safe, only to be horrified one day that every drive failed the same day. An electrical surge from a lightning strike or a faulty power supply, for example, can fry all the drives at once.