The Internet Engineering Task Forces recent approval of the iSCSI specification as a viable standard is a major milestone toward the realization of IP-based SANs.
The iSCSI protocol provides a means to transport native SCSI commands over TCP/IP, allowing storage arrays to be shared over IP and SANs to expand by utilizing Gigabit Ethernet networks. Cisco and IBM submitted the early draft for the iSCSI specification in January 2000.
Although it took more than three years for iSCSI to gain the IETFs seal of approval, the ratification of the iSCSI standard will likely spur many startups and large storage vendors to redouble their efforts to develop storage arrays, host bus adapters, TCP offload accelerator cards and management software products that support iSCSI.
The protocol faces some competition from the Fibre Channel protocol used in SANs today. That protocol has been well established in the enterprise as the standard transport medium used in SANs, providing a high level of performance and scalability. But smaller companies have been slow to adopt it because of the high cost and complexity of implementing a FC SAN. Also, FC SANs require a separate network and expertise in FC networking to manage.
The iSCSI protocol can provide a more cost-effective path for smaller companies to adopt a SAN leveraging their installed Ethernet hardware; most IT staff are already well versed in IP networking.
The iSCSI protocol can also leverage the mature security and QoS capabilities found in IP networks. And as Ethernet networks move into the 10G-bps range, iSCSI will provide much higher data transfer rates than current Gigabit Ethernet setups can handle.
The IETFs ratification clears the way for industrywide support for iSCSI, but vendors face interoperability and management challenges ahead.
With many vendors developing iSCSI components, interoperability will be a major sticking point during early adoption of the technology. Software support for iSCSI will also play a vital role in addressing storage device administration, policy management and access control.
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