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The Register Guide to iSCSI

A primer on Internet SCSI, a protocol to transport SCSI commands over IP

Published February 2008

Internet SCSI, or iSCSI, is a network protocol that transports SCSI commands packaged as IP. It runs over Ethernet and other TCP/IP capable connections, and allows storage to be accessed at block level rather than file level. That in turn means the storage appears as a local SCSI device, not a network-attached remote drive.

This is the essence of a SAN, or storage area network. SANs typically enable storage to be decoupled from the servers that use it, and can be used to share and consolidate storage, and to make it easier to manage. For example, the servers can use the SAN to share a RAID array or tape library instead of each needing one of its own.

It's been a testing time for iSCSI developers and users. Their IP-based scheme for building storage area networks (SANs) has received huge amounts of publicity and hype in recent years, starting even before it was ratified by the IETF in February 2003, yet it has failed to set the storage world alight.

Breaking into an established market is always going to be tough if you're not at least an order of magnitude better or cheaper - preferably both - than the incumbent. And not only was iSCSI slower than its rival Fibre Channel, but there were fears that it could overload IP networks or prove unreliable.

So now that the hype appears to have abated somewhat, is this a sign that the companies backing iSCSI have run out of energy and patience, or the first hint that the technology has crossed the chasm and become commonplace and accepted?