[bluGill]

For most people snapshots are enough backup. It is still useful to have an offsite backup, but realistically fire is rare enough that you can risk it, and that is about the only risk most people have (you can have your NAS in a location likely far from where a fire might break out to reduce the risk farther).

[cm2187]

Fire, malware, accidental deletions, capricious RAID controller (pre-ZFS). And that’s only the stuff that happened to me. Add power surge, theft, correlation in SSD failures (eg power on counter overflow firmware bug), damaging the array while moving, etc.

[bluGill]

Malware, accidental deletion, RAID controller issues - all things ZFS with snapshots are immune to. You can decide if the other worry you or not - the risk is not zero, but it may be acceptable. Your backups are all subject to similar issues.

[cm2187]

Snapshots don’t protect you from malware. I bet 99% of home users use the same credentials on all their machines, once a malware compromised one, the others are compromised within seconds.

[edit] also snapshots aren’t really workable for large files. Remux a movie file and now it occupies twice the space.