Très bonne parution, décidément
Local copies do not protect against site outages.
If you have a flood in your server room RAID doesn’t help.
Google File System (GFS), used throughout Google until about a year ago, takes the concept of RAID up a notch. Using coding techniques to write to multiple datacenters in different cities at once, so you only need N-1 fragments to reconstruct the data. So with three datacenters once can die and you still have the data available.