Fibre Channel is the king of enterprise storage-area-network technologies. It's fast, it can handle long distances, and it's got strong vendor support.

ISCSI, however, is the heir apparent. When it comes to new SANs, add-ons to existing systems or departmental-level installations at large enterprises that have Fibre Channel, customers increasingly are choosing iSCSI.

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And when iSCSI over 10 Gigabit Ethernet comes online, the biggest remaining hurdle to adopting iSCSI storage -- its perceived slow performance -- will fall. At that point, iSCSI will become the storage interconnection transport of choice across the enterprise.

How soon until that happens? Analysts expect support for 10G Ethernet will be built into enterprise storage arrays and servers within the next three years. This means IT executives need to start learning about iSCSI now, begin asking their storage vendors about their iSCSI road maps and begin planning for an orderly migration to iSCSI.

There are four reasons for the ascendance of iSCSI:

Cost. An iSCSI storage solution running on familiar Ethernet infrastructure costs a fraction of a high-end Fibre Channel solution in terms of the technology and the expertise needed to run it, IT experts say.

Staffing. Finding good Fibre Channel talent can be a challenge, and the scarcity drives up the cost. "It's hard to hire people with Fibre Channel expertise," says Andrew Reichman, an analyst with Forrester Research.

Compliance mandates. The growing list of industry and government mandates about the handling of data -- Sarbanes-Oxley, the Health Insurance Portability and Accountability Act, credit card regulations -- is driving companies to think out their storage and archiving policies carefully. The need to digitize documents, from simple forms to X-rays, likewise motivates companies to get their storage houses in order as inexpensively as possible without sacrificing utility and reliability.

Virtualization. "Server virtualization is a big driver," says John Sloane, analyst with Info-Tech Research Group. Many midsize companies that may not have invested in network storage because of cost now look to consolidate more of their Windows and x86 architecture with VMware. "To get the best benefit from VMware [for] disaster recovery, high availability and advanced data protection, you're really driven toward putting the virtual-machine files and data on a SAN," he says.