Backing up

[BigV]

*ahem*

ext hd has the advantage of being *doable* for all the reasons listed above. Can a hd crash? yep. chances are low. can two hds crash? yep. chances are low times low.

Plus, Cloud specifically talked about backup of her system. Not merely copies of this file and that file. Could be a substantial difference.

All the items you list have their own vulnerabilities too. In fact after you disparage the ext hd option, you then proceed to recommend four different answers. Which involve the same risk and the same device: a hard drive!

The question is how to back up a home computer. I'm unconvinced your four options answer the question.