Chapter 6. Enabling NFS over RDMA on an NFS server


If both the NFS server and clients are connected over RDMA, clients can use NFS over Remote Direct Memory Access (NFSoRDMA) to mount an exported directory.

RDMA is a protocol that enables a client system to directly transfer data from the memory of a storage server into its own memory. This enhances storage throughput, decreases latency in data transfer between the server and client, and reduces CPU load on both ends.

Prerequisites

  • The NFS service is running and configured
  • An InfiniBand or RDMA over Converged Ethernet (RoCE) device is installed on the server.
  • IP over InfiniBand (IPoIB) is configured on the server, and the InfiniBand device has an IP address assigned.

Procedure

  1. Install the rdma-core package:

    # dnf install rdma-core
  2. If the package was already installed, verify that the xprtrdma and svcrdma modules in the /etc/rdma/modules/rdma.conf file are uncommented:

    # NFS over RDMA client support
    xprtrdma
    # NFS over RDMA server support
    svcrdma
  3. Optional: By default, NFS over RDMA uses port 20049. If you want to use a different port, set the rdma-port setting in the [nfsd] section of the /etc/nfs.conf file:

    rdma-port=<port>
  4. Open the NFSoRDMA port in firewalld:

    # firewall-cmd --permanent --add-port={20049/tcp,20049/udp}
    # firewall-cmd --reload

    Adjust the port numbers if you set a different port than 20049.

  5. Restart the nfs-server service:

    # systemctl restart nfs-server

Verification

  1. On a client with InfiniBand hardware, perform the following steps:

    1. Install the following packages:

      # dnf install nfs-utils rdma-core
    2. Mount an exported NFS share over RDMA:

      # mount -o rdma server.example.com:/nfs/projects/ /mnt/

      If you set a port number other than the default (20049), pass port=<port_number> to the command:

      # mount -o rdma,port=<port_number> server.example.com:/nfs/projects/ /mnt/
    3. Verify that the share was mounted with the rdma option:

      # mount | grep "/mnt"
      server.example.com:/nfs/projects/ on /mnt type nfs (...,proto=rdma,...)
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