An Internet Small Computer System Interface (iSCSI) initiator is software or hardware that enables a host computer to send data to an external iSCSI-based storage array through an Ethernet network adapter over a Transmission Control Protocol (TCP)-based Internet Protocol (IP) network. The iSCSI initiator originates the input/output (I/O) command sequence to facilitate data transmission to the storage device, which is also known as an iSCSI target.
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Software-based iSCSI initiators are far more common than hardware-based iSCSI initiators. A software iSCSI initiator is typically part of the server operating system and uses host CPU resources to map the Small Computer System Interface (SCSI) I/O command set to TCP/IP for use by the iSCSI storage system.
A hardware iSCSI initiator is a dedicated, host-based network interface card (NIC) with built-in resources to handle the iSCSI and TCP/IP processing functions. The need for a NIC-based TCP/IP offload engine (TOE) has declined as servers have gained more powerful processing cores. A hardware iSCSI initiator may still be useful for data protection, when booting a server from a local disk, or for security, if the card has built-in encryption capabilities.
Special iSCSI name formats to identify initiators and targets include the iSCSI qualified name (IQN), extended unique identifier (EUI), and T11 network address authority (NASA).