Yep, the degraded read cost increases a lot! But it only matters if you are losing disks at a rate similar to the time it takes you to do the 1PB of i/o, and a

Yep, the degraded read cost increases a lot! But it only matters if you are losing disks at a rate similar to the time it takes you to do the 1PB of i/o, and also depends on how often you might need to serve from the data in question. I imagine that the Archive's data is tremendously cold, but I could be wrong. You can make a sensible tradeoff for any given use case. For example you might get away with a 12,8 orthogonal nested encoding, that "only" has 67% space overhead and you will be able to rebuild a single lost member without reading the entire stripe.