RAID and snapshots aren't a backup either: lightning strikes/house fires/earthquakes/floods kill all the disks together. A backup is a restorable copy in some

RAID and snapshots aren't a backup either: lightning strikes/house fires/earthquakes/floods kill all the disks together. A backup is a restorable copy in some location not sharing much fate with the primary location. Right now you might consider "all copies in one city" to have too much fate in common, but "all copies in one country" to be acceptable, or "all copies on Earth".