SCSI RDMA Protocol

SRP was published as an ANSI standard (ANSI INCITS 365-2002) in 2002 and renewed in 2007 and 2019. ==Related Protocols==

As with the ISCSI Extensions for RDMA (iSER) communication protocol, there is the notion of a target (a system that stores the data) and an initiator (a client accessing the target) with the target initiating data transfers. In other words, when an initiator writes data to a target, the target executes an RDMA read to fetch the data from the initiator and when a user issues a SCSI read command, the target sends an RDMA write to the initiator. While the SRP protocol is easier to implement than the iSER protocol, iSER offers more management functionality, e.g. the target discovery infrastructure enabled by the iSCSI protocol. ==Performance==

Bandwidth and latency of storage targets supporting the SRP or the iSER protocol should be similar. On Linux, there are two SRP and two iSER storage target implementations available that run inside the kernel (SCST ==Implementations==

In order to use the SRP protocol, an SRP initiator implementation, an SRP target implementation and networking hardware supported by the initiator and target are needed. The following software SRP initiator implementations exist: • Linux SRP initiator, available since November 2005 (kernel version 2.6.15). • Windows SRP initiator, available through the winOFED InfiniBand stack. • VMWare SRP initiator, available since January 2008 through Mellanox' OFED Drivers for VMware Infrastructure 3 and vSphere 4. • Solaris 10 SRP initiator, available through Sun's download page. • Solaris 11 and OpenSolaris SRP initiator, integrated as a component of project COMSTAR. • The IBM POWER virtual SCSI client driver for Linux (ibmvscsi), available since January 2008 (kernel version 2.6.24). Virtual SCSI allows client logical partitions to access I/O devices (disk, CD, and tape) that are owned by another logical partition. The following SRP target implementations exist: • The SCST SRP target implementation. This is a mature SRP target implementation available since 2008 via both SCST and OFED. • Linux LIO SRP target, available since January 2012 (kernel version 3.3), based on the SCST SRP target. • The IBM POWER virtual SCSI target driver (ibmvstgt), available since January 2008 (kernel version 2.6.24 • IBM's FlashSystem. • The Solaris COMSTAR target, available since early 2009 in OpenSolaris and Solaris 11. ==See also==