I have partly inherited a Linux HA cluster at the center of which currently serves a connection with DRBD 8 over IPoIB (IP over InfiniBand) between two Debian hosts. It ain't broken, so I won't fix it.
I have also noticed that DRBD 9 supports RDMA, so the question may come up whether to replace the connection with DRBD 9 over RDMA (i.e. "native" InfiniBand) in the future.
Since I don't want to run performance tests on a production system I am wondering: Are there published performance comparisons for IPoIB vs. RDMA/InfiniBand. For instance, could I expect bandwidth/latency gains from switching away from IPoIB in the orders of magniute of either 10%, 50%, or 100%, say? What could be expected?