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Internet Small Computer System Interface (iSCSI) is a protocol that permits remote access of various mediums. This in itself does nothing to suggest that iSCSI is any different than other protocols. However, the iSCSI protocol permits remote access via a standard Transmission Control Protocol/Internet Protocol (TCP/IP) line – the same type used to access the Internet. The uses of iSCSI are primarily business in nature.
iSCSI also permits the user to remotely access SCSI devices from a distance without losing much speed as compared to a physical SCSI connection. It sends the same commands used by SCSI software, however, over the network. This is true with both local area network (LAN) and wide area network (WAN) applications. Amazingly, one particular test of the iSCSI protocol allowed a user in Haifa, Israel to access a hard drive in Seattle, Washington.
iSCSI could be useful, for example, if someone were to need a file stored on a hard disk at home. If the person is on a business trip, and no one is at home to place the file onto an file transfer protocol (FTP) server, the user would not be able to gain access until someone arrived at the home computer to place the file on the server. If the file were stored on an SCSI hard drive, however, the user would be able to download the data from his home computer onto his business computer.
There are alternatives to iSCSI. Traditional storage area networks (SANs) can do much of what iSCSI does to a potentially greater degree of efficiency. Most SAN protocols, however, are not very economically sound choices, as the additional hardware often costs more than burning the data onto a floppy and mailing it to the hotel would. This makes other SAN protocols not the best choice for financially limited organizations.
iSCSI is not without faults. Its nature limits it to computers that are running an iSCSI initiator, which enables the protocol's functions. A slow TCP/IP connection would result in a slow iSCSI connection, as they are connected to each other fundamentally. This can be dramatically offset by the advent of the Gigabit Ethernet modem. This allows a fast data transfer speed, but it is also not very economically sound.
The uses of iSCSI are many, as are the disadvantages. Some of these may be nullified in the future due to advances in technology – perhaps even in iSCSI itself. It is, after all, merely a beta version of the protocol that is currently on the market.
Nice description with simple examples. Thank you! I am learning iSCSI for setting up a virtual lab.