ISCSI
In the context of computer storage, Internet SCSI (iSCSI) uses the SCSI protocol over a TCP/IP network. It enables any machine on an IP network (initiator) to contact a remote dedicated server (target) and perform block I/O on it just as it would do with a local hard disk.
The iSCSI protocol uses TCP for its data transfer. Unlike other network storage protocols, such as Fibre Channel (which is the foundation of most SANs), it requires only the simple and ubiquitous Ethernet interface (or any other TCP/IP-capable network) to operate. This enables low-cost centralization of storage without all of the usual expense and incompatibility normally associated with Fibre Channel Storage Area Networks.
Critics of iSCSI expect worse performance than Fibre Channel due to the protocol overhead TCP/IP adds to the communication between client and storage. However new techniques like TCP Offload Engine (TOE) help in reducing this overhead. And tests have shown excellent performance of iSCSI SANs, whether TOEs or plain Gigabit Ethernet NICss were used. In fact, in modern high-performance servers, a plain NIC can outperform a TOE card because fewer interrupts and memory transferss are required.
The Internet Engineering Task Force ratified iSCSI as an official standard on February 11 2003.
Functionality
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