250 billions of photos on facebook

Quite impressive number. I’m curios how many servers do they use.
Facebook used to use photo storage named Haystack, I based Eblob design solely on whitepaper of the proprietary Haystack design.

Although I removed the highest indirection level – the one where key indexes can live on separate servers, I only left in-memory and on-disk indexes.

That’s probably why Elliptics largest by number of keys storage hosts only 50+ billions (counting all 3 copies though) of objects. And that’s actually less than hundred of nodes (including all 3 replicas).