Fibre Channel is the king of enterprise Storage Area Network (SAN) 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.
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.
Analysts expect support for 10G Ethernet will be built into enterprise storage arrays and servers within the next three years. 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.
Compliance mandates: The growing list of industry and government mandates about the handling of data - Sarbanes-Oxley, credit card regulations - is driving companies to think out their storage and archiving policies carefully.
Virtualisation: "Server virtualization is a big driver," Info-Tech Research Group analyst, John Sloane, said. Many mid-sized 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 said.
Jumping the hurdles When VMware added iSCSI support last year, another hurdle to adoption fell away. "[That meant companies that] may have been on the fence about purchasing network storage or staying with direct-attached storage now have a trigger that helps them see networked storage," Sloane said.
The confluence of these trends has led Burton Group analyst, Nik Simpson, to refer to Fibre Channel as "dead technology walking".
Many customers aren't waiting for 10G Ethernet; they're finding plain old Ethernet has more than enough horsepower to get the job done. That's the case for the IT department of Clackamas County in the US, which has moved from Fibre Channel to an EqualLogic iSCSI SAN. "Everything is now on iSCSI SANs: our normal file storage, our document imaging, our Exchange System and our databases," senior IT administrator of information services for the count, Chris Fricke, said. "It's considerably cheaper not to have to deal with special cards to get it to work, and we didn't have to train people on new technologies. Our primary business goal is not baby-sitting our storage infrastructure."
Fricke isn't on 10G Ethernet yet, but he's building his storage network with 10G Ethernet in mind.
"With Fibre Channel, what we had was 1GB host bus adapters (HBA), a 1GB backplane. To upgrade all that really is a forklift upgrade to pull it out and bring in four gigs or whatever," he said. "For us, that would have been at least a half million [dollars] and not feasible. So we brought in EqualLogic for $US50,000, and we'll grow that as we need it." US law firm, Best Best & Krieger, is making the transition from HP Fibre Channel technology to iStor Networks storage for email archiving. The move to iSCSI was a no-brainer, especially because the Fibre Channel infrastructure was aging.
"For us, going from Fibre Channel to iSCSI was an upgrade," senior manager of IT for the 400-person law firm, Tim Haynes, said. Overall, iSCSI brought simplification. The use of standard networking gear for storage traffic is a major benefit, he said.
The case for Fibre Channel Of course, just as few companies have ripped out mainframes in favour of PC-based servers, enterprises will not forklift out Fibre Channel for iSCSI.
"Fibre Channel will be around for a long time to come," analyst for Enterprise Strategy Group, Tony Asaro, said. "There's a ton of investment in Fibre Channel in time, money and resources." Asaro said religious and political fiefdoms within companies could prolong a technology's life span. There were storage constituencies within organizations that had bet on Fibre Channel and would defend it to the end.
The result doesn't have to be an all-or-nothing proposition. Founder and CEO of Boston storage specialist Winslow Technology Group, Scott Winslow, estimated 10-15 per cent of his customers are on iSCSI, 30 per cent on Fibre Channel and about 60 per cent on a combination. A common misperception about iSCSI SANs is that they can run on the same Ethernet backbone as other traffic. That is technically true, but the thought of such commingling is anathema to some experts, who cite security concerns.
In reality, the recommended implementation for iSCSI storage is to run it on a separate Ethernet network. Even in that instance, the costs are less than with Fibre Channel, because IT staff are dealing with the same set of protocols and management tools across data and storage backbones.
In addition, although iSCSI on Ethernet runs on standard cards, performance-boosting and pricier HBAs still are often necessary to take advantage of 10G Ethernet. Thus, the real cost savings of moving from Fibre Channel to iSCSI may be less dramatic than some proponents say.
iSCSI it will be But even after giving Fibre Channel its due, the consensus is that iSCSI is the ultimate winner.
Analysts and users cite the upfront cost of Fibre Channel components, but stress that specialised expertise continues to be a problem. Winslow agreed companies adding to an existing storage infrastructure or moving from directattached storage, would probably prefer iSCSI over Fibre Channel.
Another iSCSI plus is that such important features as data replication and snapshots have been a la carte menu items in the Fibre Channel realm but are part and parcel of iSCSI.
Storage analysts see the writing on the wall. "We believe iSCSI will be the dominant SAN interconnect over time," the Enterprise Strategy Group's Asaro said. "Although Fibre Channel is the leading storage-networking interconnect, it is not ubiquitous because ultimately, it is expensive and complex."
Companies that have implemented it see the value in terms of performance and reliability. "However, Fibre Channel has not reached universal adoption and therefore requires either complementary or replacement technology. This is where iSCSI plays a vital role," he said.