Planning for 25 Gbps Ethernet

Before you install the optional 25 Gbps Ethernet adapter, you must review prerequisite system requirements and installation considerations before deployment.

It is helpful to be familiar with the following terms when you are considering the features of the 25 Gbps Ethernet adapter for iSCSI support.
  • Remote Direct Memory Access (RDMA)
  • RDMA over Converged Ethernet (RoCE)
  • Internet Wide Area RDMA Protocol (iWARP)
Review the following elements when you are deciding to install the optional 25 Gbps adapter.
  • The minimum software level that is needed to support the 25 Gbps Ethernet adapter features is 8.1.1.1.
  • There are two types of 25 Gbps Ethernet adapters:
    • 2-port 25 Gbps Ethernet (RoCE) adapter
    • 2-port 25 Gbps Ethernet (iWARP) adapter

    Either type adapter can be used for iSCSI connections to iSCSI hosts or storage controllers.

    Configuring a 25 Gbps adapter is no different than configuring a 10 Gbps adapter for iSCSI usage. iSCSI host attach and iSCSI storage virtualization are supported on 25 Gbps adapters as is.

    If you are undecided whether to use RoCE or iWARP in your data center, search the internet for iSCSI Extensions for RDMA to obtain more information.

  • 11 Ethernet ports are supported per node or node canister.

    To find the maximum number of Ethernet ports that can be used by the software on this node, search for Configuration Limits and Restrictions and your product name at the following website:

    http://www.ibm.com/support/

    There are 3 on-board ports plus up to 8 Ethernet ports on PCIe adapters.

  • 10 Gbps and 25 Gbps adapters are supported on the same platform.
  • Most host operating systems that are supported for the 10 Gbps adapter are also supported with the 25 Gbps adapter. To verify host operating system support, search for Configuration Limits and Restrictions and your product name at the following website:

    http://www.ibm.com/support/

  • The 25 Gbps adapter has better latency, port consolidation, and approximately 25-40% better bandwidth utilization when compared to the 10 Gbps adapter.
  • Using 25 Gbps adapters for IP replication is not currently supported.
  • iWARP adapters can talk RDMA only to iWARP adapters.
  • RoCE adapters can talk RDMA only to RoCE adapters.
  • RoCE is supported by the InfiniBand® Trade Association (IBTA) and the RoCE Alliance.
  • iWARP is supported by Chelsio and Intel.
Parent topic: Planning your network and storage network
Related concepts:
Configuring VLAN for iSCSI