Fibre Channel vs. iSCSI

For today’s IT managers, selecting a storage area network technology can feel more like a battle of acronyms than a search for a fitting solution. Although companies have long relied on Fibre Channel (FC-SANs) for storage consolidation, the recent arrival of Ethernet-based SANs (iSCSI) heralded a user-friendly – and considerably cheaper – alternative for small and cash-strapped businesses. But all that stands to change as costs associated with Fibre Channel continue to decrease, leaving today’s companies to question which storage route is most appropriate.

“In the past year, the Fibre Channel vendors have been making more of a play for the low-end of the market,” says John Sloan, a senior research analyst at Info-Tech Research Group. In fact, experts estimate that prices have plummeted as much as 60 per cent per port for Fibre Channel.

Fortunately, there are some guiding principles that can help companies choose a course of action that is most befitting their needs, expectations and pocketbooks. Among these criteria is the measure of a SAN’s overall performance. For all its promises of easy and low-cost deployment, experts say iSCSI simply can’t measure up to Fibre Channel’s speed and sophistication.

“Fibre channel still offers the highest bandwidth, the highest predictable performance for mission-critical, high-end, online transaction processing types of applications,” says Ken Steinhardt, director of technology analysis at EMC. Based in Hopkinton, Mass., EMC sells a line of network attached storage file servers, as well as a wide variety of software designed to manage, protect and share data.

Peak performance is critical to companies that depend on applications for processing sensitive financial information and confidential customer data. “If you have mission-critical applications and you have the [in-house] expertise, then Fibre Channel is great,” says David Dale, an industry evangelist at Network Appliance and chairperson of the Storage Networking Industry Association’s (SNIA’s) IP Storage Forum. Network Appliance is a Sunnyvale, Calif.-based provider of unified storage systems designed primarily for medium- to large-sized companies. As it stands, Fibre Channel’s nominal transfer rate is 2Gbps and is likely to scale to 4Gbps in the near future. iSCSI’s transfer rate, on the other hand, sits at 1Gbps.

Nevertheless, Dale warns that companies shouldn’t base their SAN selection on speed alone. After all, he says, while iSCSI is slower than Fibre Channel, it’s also 40 per cent faster than limited and costly direct attached storage (DAS). And Sloan of Info-Tech says that factors such as application workload can just as easily contribute to poor transfer rates.

“The real question is how fast is fast enough,” says Sloan, noting that differences in transfer rate are often negligible from an end-user’s perspective.

What iSCSI lacks in speed, however, it makes up for in simplicity. Whereas an FC-SAN deployment calls for the installation of a high-priced HBA and drivers, all it takes to connect a server to an iSCSI network is a Gigabit Ethernet NIC. Such ease-of-use is particularly attractive to today’s small and medium-sized businesses with limited IT resources and tight budgets. Whereas FC-SANs often demand a hefty investment in storage administrators, most IT professionals already possess a vast knowledge of Ethernet technology.

“The beauty of iSCSI is that it’s a completely ubiquitous technology; every server administrator knows how to manage TCIP networking and how to configure it so there’s a broad experience base with the technology,” says Dale.

But that kind of familiarly can also backfire, warns Bob Passmore. Vice-president of research at Gartner, Passmore says that in the case of FC-SANs, cables are situated inside a data centre that only employees are able to access. What’s more, even an ill-intentioned employee would have a tough time finding the tools needed to hack into Fibre Channel. iSCSI is another story though. “Anybody with a PC made in the last ten years and some shareware can tap in and see exactly what’s going on over that network,” says Passmore. As a result, he says companies relying on iSCSI must take additional security measures.

Fears concerning the protection of proprietary data may propel companies towards Fibre Channel but the technology is still financially out of reach for many small businesses. In fact, Passmore says that while Fibre Channel switches can cost upwards of $1,000 a port, a simple IP networking switch can be purchased for a mere $80 per port.

“Even though Fibre Channel has come down fairly dramatically, there are still small businesses that can’t afford it,” says Passmore.

It’s for this reason that experts say many companies are opting for a hybrid storage model. Small and medium-sized businesses eager to overcome storage management challenges are slowly recognizing iSCSI as a cost-effective and easy-to-deploy option. Over time, these growing companies can easily add Fibre Channel onto the infrastructure as the need arises.

At the same time, many enterprises boasting large financial investments in Fibre Channel are opting to connect remote servers using iSCSI into the very same networks.

“From an overall storage network perspective, the customer should have the flexibility to go either way and to use both [technologies],” says Steinhardt of EMC.

Hybrid models may point to the future of SANs, especially as Fibre Channel costs decrease, but experts predict it may take some time before companies catch on to the benefits of uniting both Fibre Channel and iSCSI.

And despite the obvious perks of iSCSI, there are no clear signs of it replacing Fibre Channel altogether. In fact, according to a recent Gartner report, the worldwide, external disk array revenue where iSCSI is the host connection amounted to US$48.2 million in 2004 and is projected to top US$88.1 million in 2005. However, the total external array market is projected to reach US$16 billion in 2008, with Fibre Channel representing 79 per cent of that number. iSCSI, on the other hand, will represent only a fraction of that market in 2008 US$499.7 million, according to Gartner.

Regardless of market share prognostications, however, one thing is for certain: over the next year or so, an increasing number of storage vendors are expected to offer iSCSI versions of their mainstream mid-range and low-end SAN arrays.

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