Ask HN: Facebook's Project Prism

Google has published Spanner, a new database system, paper and world has stunned again. Most interesting feature is ability to serve (transparently) from geographically seperate data centers. It's a flexible "database" for serving requests ranging from ad display to analytics to search queries. OTOH, Facebook did the global-multi-DC for analytics seemingly because they (FB) talk Hadoop only not HDFS not HBase, but Hadoop [1]. At first I thought this is excellent then I'm confused. What did exactly they do? a) improved/forked HDFS b) improved/forked HBase c) completely new FS on top of Hadoop d) completely new db on top of HDFS e) ??

[1] http://www.wired.com/wiredenterprise/2012/08/facebook-prism/