Fibre Channel: A Bus Is Born

Posted on October 01, 1997

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Fibre Channel: A Bus Is Born

The labor pains are over. Now it`s a matter of matching interfaces to applications, and here`s why there may be more fibre in your future.

John Haystead

Depending on who you talk to, you`ll hear various opinions on the current state of Fibre Channel acceptance and the overall market potential for the new interface. This isn`t surprising. Given the huge installed base of parallel SCSI, there`s a lot at stake. Many of Fibre Channel`s strongest advocates also have a vested interest in maintaining their SCSI-based business lines for as long as possible. But while some observers continue to describe Fibre Channel`s labor pains and others hedge their bets as to when it will become the big-kid-on-the-block, there is no longer any question that 1997 will turn out to be the year in which the Fibre Channel bus is finally born.

For the storage industry, the primary interest in Fibre Channel is its high-bandwidth, long-distance, multi-node arbitrary loop (FC-AL) specification. Although many end-users don`t yet know much about FC-AL, they know what their capacity and throughput requirements are. And so do major storage channel vendors (OEMs, VARs, and integrators), who have already laid plans to meet those requirements-- with Fibre Channel.

As a result, FC-AL is taking a big step toward fulfilling its promise as the de facto connectivity standard for high-speed storage access and server clustering in imaging, video, and mass data transfer applications.

"FC-AL will make its first mark in medium and high-end storage applications," says Robin Harris, senior product manager at Sun Microsystems, an early pioneer of Fibre Channel. "With the advent of universal databases, handling not only ASCII data files but graphics, video, and audio, the requirements for high-end server I/O, bandwidth and capacity are growing dramatically. Some industry analysts show these requirements doubling every 12 to 18 months, but it`s closer to every 9 to 12 months for our customers."

Multi-node connectivity and data access is another important driver for Fibre Channel. In fact, according to Anne Murphy, vice president of marketing at Storage Computer, "Our customers are more interested in FC-AL`s connectivity advantages than its bandwidth. Early implementers are looking for long-distance, campus-wide network connectivity between different host platforms. They get this with FC-AL, in addition to direct-channel-attach and high performance."

Applications Drive Acceptance

Although FC-AL`s first inroads were in high-end point-to-point RAID and other mass-storage subsystems, it is now broadening into other areas such as on-line transaction processing (OLTP), video/ graphics networks, and visual imaging systems. The requirements of these applications are diverse. For example, OLTP requires fast transfer of small blocks of data, while video-editing systems and sophisticated Internet applications need to access and move large image files quickly.

Joel Reich, manager of Fibre Channel marketing for Data General`s Clariion unit, says it`s hard to predict which applications will come next for FC-AL. Clariion sells its Fibre Channel array products to Hewlett-Packard`s UNIX Server Division and to Silicon Graphics` Visual Computing Group. HP primarily markets Fibre Channel`s distance capabilities and fault tolerance, while Silicon Graphics, which sells primarily into the scientific visual computing and entertainment markets, focuses more on Fibre Channel`s bandwidth, performance, and scalability.

FC-AV

Ed Frymoyer, president of emf Associates, a consulting firm in Half Moon Bay, CA, says the audio-visual industry is clamoring for Fibre Channel. "AV users say they will save over 50% in total storage costs by sharing resources through Fibre Channel," says Frymoyer. (emf recently published a report titled "Fibre Channel `97 and Beyond.")

One company serving the AV market is Video Media Inc., in San Jose, CA. Video Media integrated Box Hill`s Fibre Box RAID array into its Windows-NT-based "2Xstream" post-production editing and recording system for television stations and post-production video houses. Box Hill`s vice president of marketing, Carol Turchin, says that "speed is the thing for the video industry, with the magic number usually around 60 MBps."

Video Media president, Don Bennett, explains: "Our servers need to access and output multiple channels of high-quality video, usually at 20 MBps per channel. This makes Fibre Channel a de facto requirement." Bennett adds that Fibre Channel also addresses the need to access storage from various locations around their facilities, sometimes from floor to floor or between buildings.

Video Media introduced its Fibre Channel system in April, but sales have yet to pick up. Bennett says he`s not concerned. "For our customers, it`s not a fear of Fibre Channel that`s holding them back, it`s the industry`s ongoing transition from analog to digital technology that`s scaring them. It requires a lot of up-front assurances and hands-on evaluation."

Marc Friedmann, president of Prisa Networks Inc., in San Diego, CA, says the audio/visual business is clearly an early adopter of Fibre Channel. Prisa deals exclusively in Fibre Channel for the entertainment industry, selling adapters, hubs, switches, and software through the storage channel and direct to end-users. Prisa recently introduced its NetFX switch, which allows users to connect multiple loops of Fibre Channel server-to-server and server-to-storage interfaces. "We`ve found that you can no longer divorce networking from storage," says Friedmann.

However, the AV arena is a relatively small part of the overall storage market, and while Fibre Channel`s promoters are confident of capturing the video market and other high-end applications, they`re more concerned about how to position Fibre Channel for the broader storage market. "Everyone now recognizes that Fibre Channel is coming, and is rushing to be there, but no one is real clear on how end-users will use it or what will ultimately convince them to buy it," says John McIntosh, an analyst with Storage Systems Marketing Inc., a consulting firm in Boulder, CO.

Quantum`s product planning manager for high-end products, James McGrath, agrees. "The big question today is, `What`s the next value-added proposition that Fibre Channel offers that parallel SCSI can`t?`"

Storage Area Networking

Mike Fitzpatrick, a former product marketing manager at Seagate Technology and the chairman of the Fibre Channel Loop Community, says the key to Fibre Channel lies in the concept of the storage area network (SAN). Says Fitzpatrick, "The SAN concept has really woken up the industry as a whole to the promise of Fibre Channel. Instead of just technology, SANs offer a whole new level of storage solution."

As described by Sun`s Harris, SANs will allow users to transparently connect multiple storage resources on a distributed network that performs at the same level as a standalone system. "As opposed to SCSI arrays, which are basically married to their host or to a datacom network, Fibre Channel allows you to have multiple distributed storage arrays on multiple floors or in different buildings."

For many users, lack of distributed storage has been a major shortfall of parallel SCSI`s arbitration scheme, which fundamentally limits the number of devices on the bus, requiring the use of multiple device chains. SCSI`s distance restrictions have also limited its implementation as a distributed system. "The bottom line," says Frymoyer, "is that SCSI just doesn`t cut it anymore for systems requiring large numbers of distributed connections."

Another benefit of the SAN concept is that it allows system designers to take a building-block approach to storage arrays and processors, configuring individual elements to specific applications. According to Clariion`s Reich, "Unlike SCSI, Fibre Channel allows you to tailor individual elements of your total storage assets to specific applications, without trading off accessibility."

While the SAN concept is promising, advocates admit that it also requires a major change in the way enterprise-wide storage is implemented.

In fact, says Quantum`s McGrath, it means changing the overall way most users view storage, their MIS infrastructures, cabling, as well as their system-level software. "The less investment people have made in an existing architecture, the easier it will be for them to change," says McGrath, "Just as with Ethernet, this will take a long time to evolve, but the benefits are enormous."

Total Fibre Channel

To date, the FC-AL market has largely centered around host-to-target storage implementations. To ease the cost and user apprehension associated with transitioning to Fibre Channel drives, most server vendors have interfaced their FC-AL systems to existing SCSI-based storage arrays.

For example, although Storage Computer will offer FC-AL host-to-target connectivity on its SuperServer and OmniRAID lines this quarter, Murphy says they probably won`t move to total (e.g., down to the HDD level) Fibre Channel-based solutions for another 12 to 24 months. "It`s definitely on the horizon, but right now the price differential between Fibre Channel and SCSI is still not where the marketplace wants it. It`s a question of when the price points and benefits become compelling enough."

Other vendors, however, are moving more quickly. Sun, for example, has already shipped over two petabytes of RAID storage via its hybrid (e.g., Fibre Channel and SCSI) Fibre Channel Sparc storage arrays, and has a full Fibre Channel system in beta, which it plans to ship before the end of the year. Says Harris, "Full Fiber Channel provides significant additional benefits in terms of availability and performance."

For example, Harris points out that since Fibre Channel drives are dual ported, users can still access their data even if one path fails, and because the same interface is used both inside and outside the array, many storage subsystems will not require an additional dedicated controller. Harris predicts Sun`s full Fibre Channel systems will be priced no more than 10% above their first-generation hybrid systems.

Clariion has also shipped a significant quantity (over 50 TB) of hybrid Fibre Channel capacity and recently announced that Silicon Graphics will OEM Clariion`s new Fibre Channel5000 total Fibre Channel system. Hewlett-Packard also OEMs Clariion`s RAID subsystems, but HP`s initially taking the hybrid approach through Clariion`s Fibre Channel3000 line.

According to Art Lane, general manager of HP`s Enterprise Storage Solutions Division, "Although we`re extremely interested in total Fibre Channel solutions, the areas we`re mainly pursuing are high-capacity, high-transaction-rate applications such as data warehousing and OLTP. The initial firmware release of the Fibre Channel5000 product is geared more toward the very high-throughput, sustained-bandwidth RAID-3 video server market, whereas we`re more interested in RAID-5 and RAID-1."

Cost Factors

According to Fitzpatrick, from a marketing standpoint, "Fibre Channel" may not have been the best name for the interface because "many people associate Fibre Channel with high-cost fiber-optic cabling." In reality, he points out, copper is the preferred medium for inside-the-box FC-AL interconnects.

In fact, says Fitzpatrick, Fibre Channel is no more expensive than high-end SCSI. "Seagate is selling Fibre Channel drives at comparable prices to wide differential SCSI drives, and cost-effective controllers are also becoming available." While acknowledging that 4 Gbps controllers are expensive, Fitzpatrick points out that standard 2 Gbps products are already available at reasonable cost. emf`s Frymoyer predicts that "customers will be able to buy Fibre Channel protocol chips for less than $10 by 1999 and adapter boards for under $100 before 2000."

Still, Quantum`s McGrath points out that "as always, prices will be driven by supply/demand considerations and that it will take several years before FC-AL drive prices go down significantly--and they won`t reach price equality with SCSI drives until around 2006."

Although Quantum has announced that its Atlas III Fibre Channel drives will be available in the second quarter of next year, with advance shipments to OEMs in the first quarter, McGrath doesn`t expect Fibre Channel versions to reach significant volumes anytime soon. "They`re aimed primarily at the high-voltage differential SCSI market, which is only about 5% of the total market."

Quantum`s Atlas III family will also support low-voltage differential (LVD) Ultra2 SCSI. According to Skip Shapiro, Quantum`s product line manager, while there will be basically no difference between the price of their Ultra SCSI and Ultra2 SCSI drives, there will be a price delta for the Fibre Channel versions "comparable to the current price differential between single-ended SCSI and Ultra SCSI--anywhere from $50 to $150 per drive."

Overall, relative cost relates directly to system size and performance. For example, while large SCSI-based systems require multiple sets of adapters, controllers, and cabling, FC-AL systems need only one controller, which reduces costs and cabling complexity. "In some instances, users are buying additional servers not because they need more processing power, but because they can`t connect any more SCSI storage. This is the kind of economic driver that will pull Fibre Channel into the market," says Prisa`s Friedmann.

Fitzpatrick says the breakpoints are relatively simple. "If you`re dealing with a low-end four-drive system, SCSI is still the way to go, but when you get into large systems that would otherwise require multiple SCSI controllers, Fibre Channel will be more cost-effective."

The cost of Fibre Channel products is already becoming less of a factor for many potential users, and according to Sun`s Harris, there aren`t clear price/performance breakpoints for Fibre Channel and SCSI. "If you`re primarily price sensitive, cost will be a factor, but most users are more interested in data availability and performance than price."

According to Video Media`s Bennett, "For us, cost wasn`t really an issue because FC-AL was the only solution, but we still felt the costs were in line with what we would expect to pay for this level of performance." Although Bennett says he`d certainly like to see drive prices come down, he doesn`t see cost as a key factor for his customers. "It`s not a big consideration relative to their requirements and the size and scope of their facilities."

Even where "fibre" really means "fiber," cost may not be the biggest factor for users. Many companies are counting on FC-AL for fault tolerance, distributing their storage via fiber-optic links across buildings or campuses. "If you have a business-critical application where downtime represents millions of dollars worth of business, the cost of fiber is insignificant compared to the cost of your data," says Sun`s Harris.

Critical Mass and Market Draggers

According to Fitzpatrick, FC-AL will make major headway in the high-end storage market by the year 2000, "reaching equivalence with SCSI shipments in this market by 2001 to 2002." However, this segment is only the tip of the total storage market iceberg. While Frymoyer expects there will be roughly 290,000 Fibre Channel host-bus adapters and RAID boards purchased this year, "the magic number for a major impact on the market is probably around one million installations per year, which won`t occur until mid-1999." Even by 2000, Frymoyer sees only six to eight million FC-AL disk drives deployed, which will still be less than 20% of the total SCSI market.

The rate of Fibre Channel adoption has been limited by a lack of multiple drive suppliers and the need for a wider base of software and debugging products. Seagate is shipping Fibre Channel drives, but everyone agrees that second sourcing is necessary to propel the market to the next level.

Second sourcing is principally an end-user concern; however, it may well be addressed before it becomes a factor for the market. "On the OEM side, people have already put their Fibre Channel plans in place, recognizing that there will be multiple drive suppliers coming on-line concurrent with their products entering the market," says Clariion`s Reich. While Quantum`s drives are due early next year, some observers believe other manufacturers such as IBM and Fujitsu may have FC-AL drives before year-end.

Fibre Channel interoperability is also a concern for some users. Fitzpatrick acknowledges that there have been some minor interoperability issues, such as interfacing FC-AL to switched Fibre Channel networks. However, he says that these are being quickly worked out and that there aren`t any major land mines. "We`re not going through any technical challenges that other interfaces haven`t gone through," says Fitzpatrick. "Since many of the first-generation products were developed internally, it`s expected that some tweaking has to be done to ensure that they will operate properly in a heterogeneous environment, but this work is going on right now and companies are already demonstrating switches that allow you to put FC-AL loops on switched networks." Leading Fibre Channel switch vendors include Ancor, Arcxel, Brocade, and McData.

Software Challenges Ahead

Software management and support tools are also critical for any new technology, particularly one aspiring for industry-wide adoption.

Storage Systems Marketing`s John McIntosh observes that this is true for any technology that changes the overall approach to system architecture. "If all you`re doing is simple point-to-point connections, software isn`t a big deal, but when you go beyond that, particularly in terms of system area networks, it`s going to take a major commitment from software developers."

Clariion`s Reich says the industry is already starting to provide the software management tools needed to control distributed storage. "It`s a major development area and will be a key distinguishing point between different vendors` products."

While not discounting the challenges ahead, Fitzpatrick`s approach to software development is more pragmatic. "Right now, the best approach to dealing with the software issues is to just get the systems working at a basic level, then we can worry about moving on to more sophisticated solutions. As we go along, the drivers will continue to get better and the software integration issues will sort themselves out."

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What Is Fibre Channel?

Fibre Channel Arbitrated Loop (FC-AL) is an ANSI-standard serial connectivity technology designed for data- and communication-intensive storage applications such as data warehousing, data mining, on-line transaction processing (OLTP), Internet/intranet access, and film/video/broadcast implementations. Fibre Channel transfers data at 200 MBps in a dual-loop configuration or at 100 MBps in redundant mode, with future products expected to push performance to 400 MBps. Bus lengths reach 30 meters using copper cables and 10 kilometers with fiber-optic cabling. The maximum number of devices per loop is 126. Fibre Channel standards include specifications for mapping SCSI, HIPPI, IP, ATM, and other channel and network protocols.

Ultra2 Refuels SCSI

One reason for parallel SCSI`s staying power is that it continues to offer cost-effective and low-risk upgrade paths--the latest of which is Ultra2 SCSI.

Several Ultra2 SCSI products are now in beta and are expected to hit the market later this year. Using low-voltage differential (LVD) drivers, Ultra2 SCSI doubles the data rate of Ultra SCSI to 80 MBps and allows up to 16 devices to be daisy chained on a single bus. The maximum distance on a fully loaded bus is 12 meters; up to 25 meters is possible for point-to-point single-ended links. Although Ultra2 SCSI won`t provide the exponential performance improvement or flexibility advantages of Fibre Channel, it may meet the immediate needs of many users.

However, this "next-generation" SCSI may be too little too late. While acknowledging that some users will find it adequate for lower-bandwidth internal disk drives and servers, Clarion`s Reich doesn`t expect Ultra2 to impact the host-to-target market. "It still has the same basic distance and connectivity limitations of SCSI," says Reich.

XOR RAID

A key attraction of Fibre Channel for some users and storage integrators is the XOR RAID-level fault tolerance integrated directly into Fibre Channel drives, which eliminates the need for additional controllers or software.

Box Hill, for example, has enabled the XOR functionality embedded in Seagate`s Fibre Channel drives in its Fibre Box.

"It reduces overall storage costs as well as providing greater flexibility in terms of sharing channels and mobile storage," says Don Bennett, president of Video Media, an integrator of Box Hill`s system.

XOR is not unique to Fibre Channel, however. It is also being designed into some newer SCSI drives. Quantum, for example, will provide XOR assists in Ultra2 SCSI and Fibre Channel versions of its Atlas III drives.

However, Storage Computer`s Murphy says that before the recent arrival of drive-level XOR, many companies had developed their own system-level methods to provide the capabilities. "For that reason, we may actually eliminate or switch off some of these features in the drives."

"XOR may be useful in low-end systems where you can live with degraded mode performance, but high-bandwidth users are working with RAID-3 systems, not RAID-5, and embedded XOR doesn`t support RAID-3," says Clariion`s Reich.

John Haystead is a freelance writer in Hollis, NH.


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