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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?

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have you seen these presentations? https://www.linbit.com/en/drbd-9-over-rdma-with-micron-ssds/ http://downloads.openfabrics.org/Media/Monterey_2015/Tuesday/tuesday_09_ma.pdf

InfiniBand is just a specific network architecture offering RDMA but your performance will depend on what type of applications your are running. My experience is based on academic/research systems mostly using MPI based applications. In certain cases I have seen RDMA performing 20% better than IPoIB. But I am not aware of any such benchmarking but there are plenty of academic papers written and also vendor white papers. If you are just thinking about I/O then consider: file sizes, number of reads vs. writes. RDMA usually provided a big benefit for random small reads but only a small benefit for writes. You might want to read up on RoCE (RDMA over Converged Ethernet) and InfiniBand native RDMA.

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  • Thx, esp. for the 20% quantity. The application that is running on top is PostgreSQL. (Its pgdata resides on the DRBD device.) – rookie09 Oct 2 '17 at 11:04
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    Yes to all that. You can't go faster than the disks in your system, but assuming you're sure the disks are faster than the network they're replicating over, then you're probably going to be able to squeak some more performance out of the system switching to RDMA. – Matt Kereczman Oct 3 '17 at 2:19
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    Here is another (alternative) explanation of RDMA that might be of an interest for you starwindsoftware.com/… – Net Runner Oct 6 '17 at 7:32

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