IP Storage is a storage device which has the capability of communicating over an IP network. The term IP Storage is usually identified with a storage device which provides block-level I/O services rather than file access services. Derived from the original meaning, the term IP Storage is sometimes used to refer to an IP SAN.
The benefit of utilizing IP technology is its cost efficiency. Having been used for several decades, IP technology is highly mature. IP family protocols have been standardized and cheap hardware products have wide interoperability. The market has a number of excellent administration tools and educated administration personnel for IP technology. Designing and operating SANs on top of IP technology is much cheaper and easier than with Fiber Channel technology. Thus IP technology is sometimes considered to be replacement of Fiber Channel technology in entry-level SANs.
Internet SCSI (iSCSI), Internet Fiber Channel Protocol (iFCP) and Fiber Channel over Internet Protocol (FCIP) are three major network protocols used for IP Storage. iSCSI transmits the SCSI protocol over IP networks by encapsulating SCSI data in TCP/IP packets. That is, the idea of iSCSI is to replace classical SCSI bus cables with IP networks. iSCSI is used mainly for transferring data between servers and storage devices and among storage devices. A storage device which communicates over the iSCSI protocol is often called an iSCSI target, whereas a server which accesses such an iSCSI device is called an iSCSI initiator. In contrast, iFCP and FCIP can encapsulate Fiber Channel frames in TCP/IP packets. These protocols are usually implemented in network devices such as Fiber Channel switches and routers, thus enabling bridging two or more Fiber Channel SANs by the use of IP networks. Although iSCSI and iFCP/FCIP are both IP storage techniques, they are used in real systems in different ways. That is, iSCSI is mainly used for constructing a local SAN at low cost, whereas iFCP and FCIP are utilized for integrating remote Fiber Channel SANs (often called SAN islands.)