The Internet Small Computer System Interface, or iSCSI, is an IP-based protocol for transmitting data and linking data storage facilities. iSCSI works for transmitting data over several types of networks, including LAN (local area networks) and WAN (wide area networks), as well as the Internet itself. iSCSI is also a SAN (Storage Area Network) protocol, which can allow companies to utilize data center storage arrays to consolidate their data. Doing so can make it look as if they are utilizing local hard disk storage versus a data center storage, due to the improved performance in data retrieval that a SAN provides.
The first iSCSI storage device was introduced for use with the Windows NT, 2000, and Linux operating systems in 2001 by IBM. Since then, iSCSI devices have been made available for other operating systems, including Solaris, NetWare, VMware, macOS, NetBSD, and HP-UX. Most iSCSI devices are hard disk based, but there are also some iSCSI tape and medium changer devices on the market as well.