"Facebook is storing old photos in special cold storage halls, Zucky ziggurats housing racks filled with MAID (massive arrays of idle drives) using erasure coding and anti-bitrot scanning to increase storage density and lower power costs while providing faster-than-tape access.
Some two billion photos are shared every day on Facebook and the number is growing; Facebook doesn't disclose the rate though, and they need to be instantly available. So it has built itself two specialised facilities from the ground up to store them..."
(Get More Information . .)