SCSI RDMA Protocol

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The SRP (SCSI RDMA Protocol), also known as the SCSI Remote Protocol, allows for the RDMA transfer of SCSI commands and data across a low-level network layer such as Infiniband verbs, bypassing system and network overhead, such as teh TCP/IP stack.

As with iSer, there is the notion of a target (a physical storage device) and an initiator (a client accessing the target), with the target performing the actual data movement. In other words, when a user writes to a target, the target actually executes a read from the initiator and when a user issues a read, the target executes a write to the initiator.

Per user experience evidenced on various mailing lists, bandwidth-intensive operations seem to perform better with SRP (which uses the SCST layer) than iSer (here referenced as STGT). Although some have reported that they see better IOP performance with iSer.

Another benefit of SRP is that it is supported in both Windows (with the WinOF Infiniband stack) and Linux (OFED Infiniband stack).