remote DMA (SAN) (RDMA)

Remote Direct Memory Access (RDMA) is a technology with which data located in the main memory can be exchanged between computers or servers without involving the operating system. An example is the fast and transparent data transfer for host bus adapters( HBA) in Fibre Channel( FC).

To make server-to-storage and server-to-server communications as fast as possible, the host bus adapters (HBAs) serving as interfaces to the optical fibers require a special transport protocol with minimal overhead. RDMA meets this requirement. It supports data transmission into and out of a server by implementing a transport protocol on the network card. Through this technique, RDMA can read application data from the main memory of one computer and read it into the main memory of another computer in such a way that it is immediately available to the application layer. This procedure is performed without using a remote system and is characterized by direct transparent data transfer to the target memory at constant speeds of 100 MByte/s and low latency.

Remote Direct Memory Access (RDMA) works with different network protocols. For example, there is RDMA over Converged Ethernet( RoCE), the Internet Wide Area RDMA Protocol, and Infiniband. It supports High Performance Computing( HPC) and can be used in converged infrastructures in data centers and with supercomputers, as well as wherever lowest latency and highest transfer rates are required.