3) IIRC most tape storage technolgies are closed source. FB has been heavily pushing their open compute project. Using BDs get them past a lot of licensing problems.
and LTO has way less licensing problems than Blu-ray and LTO-6 has a max of 2.5TB. LTO is also guaranteed to to read tapes from 2 generations earlier and write one generation earlier. Blu-ray has no such long term guarantee.
