Fibre Channel SANs: 4G or Not 4G?

QLogic and Vixel are pushing 4-Gbit/s Fibre Channel for SANs - but they're meeting resistance

March 15, 2003

6 Min Read
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Two Fibre Channel vendors -- QLogic Corp. (Nasdaq: QLGC) and Vixel Corp. (Nasdaq: VIXL) -- are pushing for the industry to adopt 4-Gbit/s Fibre Channel for the next generation of SANs, but early in their campaign they're meeting resistance.

As recently as six months ago, Fibre Channel vendors and their storage partners appeared to have reached a consensus that 10 Gbit/s would be the next step up after the current generation of 2-Gbit/s FC. The rationale for this was for FC to keep pace with Ethernet, which is jumping from Gigabit Ethernet to 10-Gig Ethernet (see 10-Gig SANs).

However, recent discussions among members in the Fibre Channel Industry Association (FCIA)'s Speed Forum working group [ed. note: of which Keanu Reeves is actually not a member] have raised the issue of putting 4-Gbit/s FC on the roadmap as a SAN fabric technology. Currently, the FCIA defines 4-Gbit/s Fibre Channel only for internal system connectivity.

The 4-Gig SAN movement is early, and there's a distinct possibility that switches and host bus adapters (HBAs) that support this technology will never come to market. But the concept has two ardent backers in QLogic and Vixel, which are trying to make the case for why the industry should go to 4 Gig as an interim hop before it goes to 10-Gig Fibre Channel.

"The short version is, 10-Gig adoption is going to be a little longer than everyone anticipated originally, because of the cost," says Frank Berry, QLogic's VP of corporate marketing. "People are now figuring out that there's gap between 2 Gig and the adoption of 10 Gig... so at a certain point, 4 Gig starts to look a lot more interesting."The 4-Gig supporters point to several benefits of using this technology for SAN fabrics:

  • It would double throughput but be only slightly more expensive than 2-Gbit/s FC, because 4 Gig would be able to use many of the same components as the current generation products, whereas even at high volumes, 10-Gig would be an estimated three to five times the cost of 2-Gig.

  • It would fit into the existing headroom of the PCI-X 1.0 host bus specification, which has 1-Gbyte/s throughput (see diagram, below).

  • High-end drive manufacturers, including Seagate Technology Inc. (NYSE: STX) and Hitachi Ltd. (NYSE: HIT; Paris: PHA), are planning to adopt 4-Gbit/s interfaces for future generations of FC disk drives, so the SAN industry could see economies of scale in providing front-end 4-Gig SAN connectivity.

  • 10-Gig FC is not backward compatible with 1- or 2-Gbit/s FC, whereas 4 Gig would be.

Figure 1:

The first 4-Gbit/s FC hard disk drives are expected to arrive in early to mid-2004, and if the industry gets behind the technology for SAN connectivity that's roughly the same timeframe in which 4-Gbit/s SAN switches and HBAs would hit the market. We should note here that QLogic and Vixel are especially interested in promoting 4-Gbit/s Fibre Channel SANs because they're reportedly already developing this technology for storage subsystem vendors and disk drive manufacturers and would be able to leverage that existing investment for the broader SAN market. (Neither QLogic nor Vixel has announced 4-Gbit/s FC products.)

But to get the FCIA to officially adopt 4-Gbit/s FC as the next generation for SAN fabrics, QLogic and Vixel will need to secure the majority backing of the 28 other voting members of the association. And today, the votes aren't there, admits Stuart Berman, CTO of Vixel.

"The issue here is whether the current fabric vendors are going to get on the boat and do 4 Gig or not," he says [ed. note: sounding an awful lot like Colin Powell].Today, the answer would be they are not planning to get on the boat. The two primary suppliers of FC switches today are Brocade Communications Systems Inc. (Nasdaq: BRCD) and McData Corp. (Nasdaq: MCDTA), and neither of these companies appears interested in adopting 4-Gbit/s FC -- at least, not yet.

"From our perspective, it's going to be a movement from 2 Gig to 10 Gig," says Chris Ilg, McData's senior manager of strategic marketing. "When we talk to our large OEM disk array vendors, we haven't heard anyone talk about putting 4 Gig there."

He says McData will initially use 10-Gbit/s FC for inter-switch links (ISLs) to reduce congestion across high-speed core SAN backbones; only later, he says, will it appear for server or storage array connectivity. Ilg adds, however, that if 4 Gig does begin to gain momentum, "we could easily come out with 4-Gig support for our directors... Our architecture can support that."

Brocade, meanwhile, is said to be strongly opposed to 4-Gig. Industry sources say this is because the company has already invested resources in developing 10-Gbit/s FC. It also has two enormous tasks occupying its attention: integrating recently acquired virtualization switch startup Rhapsody Networks, and fending off the advances of Cisco Systems Inc. (Nasdaq: CSCO) in this market (see Brocade Reupholsters Rhapsody, Cisco and EMC Edge Closer, Sprint Puts Cisco to Test, and Cisco Gets Set).

"Brocade is terribly strapped right now," says one industry executive, who did not want to be identified. "They need another initiative like 4 Gig like they need a hole in the head."Officially, Brocade says it's not opposed to any direction yet and is "looking closely at the matter of 4 and 10 Gbit/s," says a company spokeswoman.

For its part, HBA vendor Emulex Corp. (NYSE: ELX), which has already staged demonstrations of 10-Gbit/s FC technology, doesn't see much value in moving to 4-Gig FC (see Emulex Cooks Up 10-Gig FC Demo).

"From where I sit, the clear next step in Fibre Channel SANs is 10 gigabit," says Mike Smith, executive VP of worldwide marketing at Emulex. "It's not as far away as a lot of folks think."

He says switch vendors are planning to demonstrate products running 10-Gbit/s FC later this year, and notes that as Ethernet goes to 10-Gig the cost of the optical transceiver interfaces, which are a large part of the overall cost, will drop. "I haven't seen any of the optics guys say they're going to do a 4-Gig optics... so the cost differential between 4 and 10 may not turn out to be that great," says Smith.

Others in the industry seem to be taking a wait-and-see stance, although many see advantages in moving to 4-Gig FC. "Once the electronics for 4 Gig are developed to support this move [to 4-Gbit/s Fibre Channel drives], then it has the potential to creep out from the back of the RAID controller into the network infrastructure," says Shriraj Gaglani, at Broadcom Corp. (Nasdaq: BRCM), which recently acquired the assets of bankrupt FC switch vendor Gadzoox (see Broadcom Switches on FC).QLogic and Vixel executives stress that they're not opposed to 10-Gbit/s FC, just that they believe 4-Gig would be a more cost-effective path for the next generation of SANs.

"Our sense is there's a pretty big disconnect between the probable introduction of 4 Gig versus 10 Gig," says Roger Klein, VP of product marketing at QLogic. "The question is, is it appropriate to have a 'speed bump' on the road to 10 Gig products?"

That's the question FCIA members will attempt to answer in the next few months -- and it remains to be seen whether the 4-Gig SANbackers will win the day.

Todd Spangler, US Editor, Byte and Switch

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