Native RDMA support for Ceph is still a ways off. The current implementation requires disabling Cephx authentication, which is a no-go in any environment where you can't completely trust every client (e.g. "cloud", where most current deployments/users live). It also hasn't seen much development since the initial proof-of-concept (still highly experimental).

That said, IPoIB should work just fine, and the main bottleneck currently is (Ethernet) latency. I'm running a couple of 1,6PB clusters (432 * 4TB) and can only get 20-60MBps on a single client with a 4kB block size, but got bored of benchmarking after saturating 5 concurrent 10Gb clients with a 4MB block size.

I do expect the RDMA situation to improve substantially over the next year or so, even if authentication will still be unsupported. The latter generally isn't a problem in HPC where stuff like GPFS lives (where you also have to trust every client). And they clearly want that market now that CephFS is finally deemed production ready.