Storage Infrastructure
network. Even in that instance, the costs are less than with Fibre Channel, because IT staff is dealing with the same set of protocols and management tools across data and storage backbones. The Gem Group maintains separate storage and data networks for security and performance reasons "but the switches are interconnected," Smith says. "We have the data center and one data closet, so we have some physical servers and some virtual servers in the secondary closet along with a secondary SAN that's connected at fiber-optic speeds. That let us do longer distances between data sites without degradation," he says. 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. Winslow Technology's Winslow estimates in some cases the savings is more like 10 percent to 15 percent than the higher figures some pundits cite. It seems certain that the cost of Fibre Channel components will fall as iSCSI storage gains ground, further narrowing the price gap. Although purists may not be pleased, a hybrid Fibre-Channel-andiSCSI approach is finding acceptance in many sites. Winslow, who sells Compellent products, says several of his customers use Fibre Channel for their main storage repository but plug in additional iSCSI cards for failover storage needs.
Ă la carte menu items in the Fibre Channel realm but are part and parcel of iSCSI. EqualLogic's storage solution brought Leo A. Daly advanced features, including snapshotting and bit-level replication between devices, for which they would have had to pay extra in the Fibre Channel world, Christiansen says. Snapshotting lets the system roll back to data at a set period in time in case of a failure. believe that Clackamas County's Fricke also stressed this point: iSCSI SANs will "When we bought Fibre Channel, we couldn't even afford snapshotting or replication." Both capabilities be new SAN are now deployed at no extra cost. buildouts and IT experts also say that with implementation knowwill not replace how, iSCSI can rival current Fibre Channel speeds. The Gem Group's Smith opted for HP switches that Fibre Channel. will support 10G Ethernet if the company needs to Source: Enterprise go that route, but he also went with enterprise-class Strategy Group connections rather than standard network interface cards to optimize performance. "We do multiple connections, on each server. I go with a two-port QLogic card with two 1GB connections. You can connect that into the SAN in active/active mode. People say Fibre Channel is faster at two or four gigs, but I already have two gigs with iSCSI," Smith says. Storage analysts see the writing on the wall. "We believe that iSCSI will be the dominant SAN interconnect over time," the Enterprise Strategy Group's Asaro says. "Although Fibre Channel C MPanies CoMPanies MP that haV ha e is the leading storageFibre Channel SANs networking interconnect, Fibre Channel SANs and NAS and iSCSI it is not ubiquitous because and iSCSI SANs SANs ultimately, it is expensive and complex." Companies that 25% 13% have implemented it see the value in terms of performance and reliability. "However, Fibre Channel has not 33% 43% reached universal adoption and therefore requires either complementary or replacement technology. 42% 45% This is where iSCSI plays a vital role," he says. Sloane of Info-Tech agrees. "There is tremendous growth opportunity. For iSCSI there is nowhere to go but up." CIO
42%
will you move from a fibre CHaNNel SaN to iSCSi SaN?
exPerts agree: isCsi it will be
We will replace FC SANs with iSCSI to a significant extent
But even after giving Fibre Channel its due, the We will replace FC consensus is that iSCSI is the SANs with iSCSI to ultimate winner. some extent Analysts and users cite We will not replace the upfront cost of Fibre FC SANs with iSCSI– Channel components, but iSCSI SANs buildouts stress that specialized will be added. expertise continues to be a problem. Winslow agrees that companies adding to an existing storage infrastructure or moving from direct-attached storage, more likely will opt for iSCSI over Fibre Channel. Another iSCSI plus is that such important features as data replication and snapshots have been
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Barbara Darrow is a Boston-area freelance writer. Send feedback on this feature to editor@cio.in
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