The Internet Small Computer System Interface (iSCSI) is SCSI over IP that sends SCSI commands using the TCP/IP protocol suite. This means that the SCSI commands are encapsulated on top of IP, which commonly runs on Ethernet. FC SANs typically have a very high cost because the FC equipment is specialized. In comparison, iSCSI provides a cost-effective alternative to FCs because of the low cost of Ethernet equipment; also, the abundance of Ethernet experts, as compared to FC, keeps the administration costs low. Earlier iSCSI was subject to lower performance due to the noisy nature of TCP/IP, causing higher protocol overload. Over the years, iSCSI performance and efficiency has improved. In fact, with the latest 10 Gbps implementation and future 40 Gbps/100 Gbps implementation with Data Center Bridging (DCB), it is now a serious competitor to FC.

iSCSI consists of the following:

• Hard disk arrays: They provide raw storage capacity.
• Storage processors: They manage hard disks and provide storage LUNs and masking for the servers.
• Ethernet switches: They provide connectivity between storage processors and server HBAs.
• iSCSI host bus adapters: They are installed in a computer and provide connectivity to the SAN. Most operating systems provide software implementation of iSCSI in order to utilize the regular Ethernet NICs, eliminating the need for hardware iSCSI HBAs.