In a world where Internet Protocol (IP) dominates local and wide area networks, the data storage requirements grow unabated; it seems inevitable that these two forces converge. The Internet Small Computer Systems Interface (iSCSI) protocol unites storage and IP networking. iSCSI enables the transport of block-level storage traffic over IP networks. It builds on two widely used technologies - SCSI commands for storage traffic over IP networks. It builds on two widely used technologies - SCSI commands for storage and IP protocols for networking. iSCSI is an end-to-end protocol for transporting storage I/O block data over an IP network. The protocol is used on servers (initiators), storage devices (targets), and protocol transfer gateway devices. iSCSI uses standard Ethernet switches and routers to move the data from server to storage. It also enables IP and Ethernet infrastructure to be used for expanding access to SAN storage and extending SAN storage and extending SAN connectivity across any distance. This paper presents general overview of iSCSI, outlining its introduction, details of the protocol, its features, user benefits, and several typical deployment scenarios and applications.
The SCSI protocols widely used to access storage devices. The iSCSI protocol is a transport for SCSI over TCP/IP. SM-2 defines an architecture model for SCSI transports, and iSCSI defines such a transport on top of TCP/IP. Other SCSI transports include SCSI Serial and Fibre Channel Protocol (FCP). Until recently standard networking hardware (Ethernet) and IP-based protocols could not provide the necessary high bandwidth and low latency needed for storage access. With the recent advances in Ethernet technology, it is now practical from a performance perspective to access storage devices over an IP network. 1Gb Ethernet is now widely available and is competitive with current 1 and 2 Gb Fibre Channel technology. 10Gb Ethernet will soon also be widely available. Similar to FCP, iSCSI allows storage to be accessed over a storage area network (SAN), allowing shared access to storage. A major advantage of iSCSI over FCP is that iSCSI can run over standard off-the-shelf network components, such as Ethernet. Furthermore, iSCSI can exploit IP-based protocols such as IPSec, for security and Service Location Protocol (SLP) for discovery. A network that incorporates iSCSI SANs need use only a single kind of network infrastructure (Ethernet) for both data and storage traffic, whereas use of FCP requires a separate kind of infrastructure (Fibre Channel) for storage (Fig.2). IP based SANs using iSCSI can be managed using existing and familiar IP-based tools such as Simple Network Management Protocol (SNMP) whereas FCI SANs require specialized management infrastructure. Furthermore, iSCSI-based SANs can extend over arbitrary distances, just like TCP, and are not subject to distance limitations that currently limit FCP.