Internet SCSI (iSCSI) allows standard SCSI commands to be passed between host systems (initiators) and storage devices (targets) over a TCP/IP net-work.130 iSCSI is a block-level storage protocol that lets users create a separate storage network using Ethernet. Because iSCSI uses Ethernet, it does not suffer from the complexity and distance limitations of other storage proto-cols.
Unlike other storage area network technologies, iSCSI uses standard Ethernet switches, routers and cables and the same Ethernet protocol de-ployed for communications on LANs (TCP/IP). Because iSCSI uses SCSI commands, relying on Ethernet only to transport the SCSI commands, oper-ating systems see iSCSI-connected devices as SCSI devices and are unaware that the SCSI device sits across the room or across town. When SCSI is mapped to TCP/IP through the iSCSI layer, SCSI is freed from its parallel bus structure, allowing users to extend network storage using Ethernet.
iSCSI can be supported over any physical media that supports TCP/IP as a transport, but today's iSCSI implementations are on Gigabit Ethernet. The iSCSI protocol runs on the host initiator and the receiving target device. iSCSI can run in software over a standard Gigabit Ethernet network interface card (NIC) or can be optimized in hardware for better performance on an iSCSI host bus adapter (HBA).
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