Yes, the needs for archives (sole copy) and backups (additional copies of live data) are different. > It is possible to use RAID-5/RAID-6-like encoding schemes

Yes, the needs for archives (sole copy) and backups (additional copies of live data) are different. > It is possible to use RAID-5/RAID-6-like encoding schemes that can survive the complete destruction of 1 or even 2 storage centers while using less tapes than with simple copies, but such encoding schemes can be used only by very large organizations, which use more than 3 separate storage centers. Scenarios where two storage centers are destroyed—that’s extreme. The most paranoid scenarios I’m normally willing to entertain are along the lines of one data center burns to the ground in a generator fire, and somebody drives a truck full of backup tapes into a ditch and they’re all covered with mud and sand. Tapes have a high enough failure rate that you benefit from forward error correction and you benefit from planning to handle individual tape failures. This includes stuff like the tape leader breaking, somebody losing a tape, damage during transport, water damage in storage, etc. There’s a layered approach here, where you plan for different disasters at different levels of the stack. Each layer exposes some certain failure rate to the layer above it, and deals with some certain failure rate at the layer below it. When I think of backups, I often imagine a top-level data storage system that has a geographically distributed hot backup, and then an offline cold backup. This lets you survive complete destruction of one data center, or lets you survive a catastrophic software bug that destroys data (and a bunch of tapes are damaged on top of that). Pretty good baseline, IMO.