Also ceph (& swift) are known to scale well in prod. clusters with over 30+ PB of data (at least looking at CERN's cluster) and the latest version of RGW does support geographic redundancy for S3 like apis
+1 for Ceph. We're running several ~3.5 PB clusters in production. We've not taken advantage of the new RGW features in Jewel, but it works well as an object storage solution.
