iSCSI Extensions for RDMA

The iSCSI Extensions for RDMA (iSER) is a computer network protocol that extends the Internet Small Computer System Interface (iSCSI) protocol to use Remote Direct Memory Access (RDMA). RDMA is provided by either the Transmission Control Protocol (TCP) with RDMA services (iWARP) that uses existing Ethernet setup and therefore no need of huge hardware investment, RoCE (RDMA over Converged Ethernet) that does not need the TCP layer and therefore provides lower latency, or InfiniBand. It permits data to be transferred directly into and out of SCSI computer memory buffers (which connects computers to storage devices) without intermediate data copies and without much of the CPU intervention.An RDMA consortium was announced on May 31, 2002, with a goal of product implementations by 2003.The consortium released their proposal in July, 2003.The protocol specifications were published as drafts in September 2004 in the Internet Engineering Task Force and issued as RFCs in October 2007.The OpenIB Alliance was renamed in 2007 to be the OpenFabrics Alliance, and then released an open source software package.The motivation for iSER is to use RDMA to avoid unnecessary data copying on the target and initiator.The Datamover Architecture (DA) defines an abstract model in which the movement ofdata between iSCSI end nodes is logically separated from the rest of the iSCSI protocol; iSERis one Datamover protocol. The interface between the iSCSI and a Datamover protocol, iSERin this case, is called Datamover Interface (DI).