Yes, Rex-Ray is EMC specific. Take a look at Robin Systems (https://robinsystems.com/) for stateful containers. They have examples of running hadoop, cassandra, mongodb, etc all on commodity hardware.
That's not really accurate I think. RexRay is also supporting non-EMC solutions: https://github.com/codedellemc/rexray#storage-provider-suppo...
>"We'll probably opt for this config near-term for our web-server SSR cache."
What is an SSR cache?