HP ML530 RDMA protocol: improving network performance - Page 11
SCSI RDMA Protocol, InfiniBand link operation, Conclusion
UPC - 720591250669
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SCSI RDMA Protocol SCSI RDMA Protocol (SRP) encapsulates SCSI commands over InfiniBand for SAN networking. Operating from the kernel level, SRP allows SCSI commands to be copied between systems via RDMA for low-latency communications with storage systems. InfiniBand link operation Since some network devices can send data faster than the destination device can receive it, InfiniBand uses a queue pair (one send, one receive) system similar to the one for RDMA over TCP. InfiniBand queue pairs may be located in the HCA or TCA of each device or, if necessary, in main memory. When a connection between two channel adapters is established, the transport layer's communications protocol is selected and queue pairs are assigned to a virtual lane. The transport layer communications protocol can be implemented in hardware, allowing much of the work to be off-loaded from the system's processor. The transport layer can handle four types of data transfers for the Send queue: • Send/Receive - Typical operation where one node sends a message and another node receives the message. • RDMA Write - Operation where one node writes data directly into a memory buffer of a remote node. • RDMA Read - Operation where one node reads data directly from a memory buffer of a remote node. • RDMA Atomics - Combined operation of reading a memory location, comparing the value, and changing/updating the value if necessary. The only operation available for the receive queue is Post Receive Buffer transfer, which identifies a buffer that a client may send to or receive from using a Send, RDMA Write, or RDMA Read data transfer. Conclusion RDMA operations can provide iWARP functionality to today's Ethernet networks and relieve the congestion that 10-Gb Ethernet might otherwise cause. High-performance infrastructures such as InfiniBand use RDMA as a core function to efficiently handle high data throughput that previously required specialized networks. HP is a founding member of the RDMA Consortium, an independent group formed to develop the architectural specifications necessary to implement products that provide RDMA capabilities over existing network interconnects. Many of the concepts and technologies leveraged for RDMA come from high-end servers, such as HP NonStop and SuperDome servers, and from established networking used in storage area networks (SANs) and local area networks (LANs). HP has led the development in networking and communication technologies, including cluster interconnects such as ServerNet, the Virtual Interface (VI) Architecture, and InfiniBand, which represent the origins and evolution of RDMA technology. Today, HP is at the forefront of the RDMA technology initiative and is a trusted advisor on future data center directions that provide lasting value for IT customers. HP is committed to support RDMA as applied to both Ethernet and InfiniBand infrastructures, and to help customers chose the most costeffective fabric interconnect solution for their environments. 11