As the storage networking protocol seems to be hitting its stride, new challenges arise
Storage-area networks (SANs), which connect multiple servers to multiple storage devices, are gaining acceptance among government agencies for their flexibility and affordability.
From disk arrays to network switches, demand for Fibre Channel gear has increased 20 percent annually, fueled by agencies' preference for SANs over storage systems that connect to only one server at a time. Early resistance from information technology shops to the esoteric Fibre Channel protocol has mostly disappeared thanks to growing familiarity and falling prices.
But government IT managers are beginning to ask of Fibre Channel, "What have you done for me lately?" Speed and distance limitations are their two categorical concerns.
The recent doubling of Fibre Channel's throughput speed is good but not enough for some power-users. Even mainstream federal shops have a reason to gripe. Many of them want to cut costs by consolidating scattered data centers or improve their business continuity preparations by backing up data to a safer, offsite location. In both cases, Fibre Channel's 10 kilometer distance limits them.
Vendors are working on both of those problems, but like the original Fibre Channel specifications, solutions will take some time to reach the market. In the meantime, Fibre Channel alternatives such as iSCSI or InfiniBand might be able to use that window to gain some traction.
Fibre Channel was originally designed to move information from mainframes to disk arrays and tape drives. It has been enhanced to become an American National Standards Institute standard defining data link interfaces used for a variety of platforms and for transmissions over fiber-optic and coaxial cables.
The original and most common version of Fibre Channel supports 1 gigabit/sec transmissions, but a recent enhancement boosted the top speed to 2 gigabits/sec.
The National Center for Supercomputing Applications in Urbana-Champaign, Ill., has 40 terabytes of information stored on an IBM Corp. p690 server; another 170 terabytes support its TeraGrid project, designed to distribute computing among five research facilities. At the end of 2002, NCSA installed 2 gigabits/sec Fibre Channel links, supported by Silkworm 12000 and Silkworm 3600 switches from Brocade Communications Systems Inc., but center officials are interested in even faster speeds.
"Our computing requirements are so great that we are usually ready to deploy higher-speed technologies as soon as vendors are ready to deliver them," said Michelle Butler, technical program manager at NCSA. She expects the center's storage requirements to reach 500 terabytes in a few years.
A few factors are driving the growing requirements for storage network bandwidth. Increasingly, applications and database management systems process complex, multimedia information that requires faster throughput. Agencies also are consolidating autonomous servers, and even full data centers, so central SANs are housing larger volumes of data.
The Air Force Materiel Systems Group, which supports 150,000 users, is one such organization. The agency is in the process of building four data centers that will replace 60 data centers. The four consolidated sites will be at Wright-Patterson Air Force Base in Ohio, Robins Air Force Base in Georgia, Tinker Air Force Base in Oklahoma and Hill Air Force Base in Utah.
The centers at Wright-Patterson and Tinker should begin operating during the summer, and the entire migration is slated for completion by the end of 2004.
"We anticipate working with at least 100 terabytes of information at each data center, so [Fibre Channel] connections will be a necessity," said Fred Altum, a program manager at the Air Force Materiel Systems Group. To overcome Fibre Channel's distance limitation, Altum said the group is looking at products that use a new standard called Fibre Channel over IP.
Two higher-speed Fibre Channel options, 4 gigabits/sec and 10 gigabits/sec, are emerging. Work on the 4 gigabits/sec standard began two years ago, and a version that supports internal switching within SAN switch is expected to show up in vendors' products by the end of the year. In June, suppliers crafted a standard that supports 4 gigabits/sec speeds for external connections to other switches, disk arrays and tape systems. Compliant products are expected to ship next year.
"A chief benefit with the 4 gigabits/sec approach is it is backwardly compatible with 2 gigabit and 1 gigabit connections," said Bob Williamsen, director of strategic marketing at McData Corp., which sells Fibre Channel switches.
Because of the complexity of a tenfold boost in the transmission rate, the 10 gigabits/sec option is not backwardly compatible and therefore requires that users put in new links on both ends of a connection. Compliant products are expected to ship next year.
Customers' interest in a 10 gigabits/sec option is unclear. Initial expectations are that such links will cost about three times more than 2 gigabits/sec connections, while 4 gigabits/sec links will cost only 25 percent to 50 percent more.
The 10-gigabit approach has supporters. "The need for higher-speed connections is evident mainly between SAN-to-SAN switches, and 4 gigabits/sec does not offer enough of a performance boost to solve that problem," said Bill Erdman, director of marketing at Cisco Systems Inc.
Fibre Channel has been gaining acceptance but still is not a mass-market technology. Pricing is one reason why many organizations have not adopted it. Customers have to pay about $40,000 to $50,000 to install a Fibre Channel SAN, which doesn't make a lot of sense if they have only a handful of $5,000 servers, according to Rahul Patel, product line manager at Broadcom Corp., which sells broadband hardware. Fibre Channel pricing has been decreasing about 10 percent per year, a trend that should continue and help agencies justify SAN investments.
Product interoperability has also been a problem that groups such as the Storage Network Industry Association have been trying to tackle. "The industry has made a lot of progress with baseline connectivity among SAN products so users can now get most products connected," said Steve Daheb, director of product marketing at Brocade. "But vendors often add their own little extensions to the baseline features so it can be difficult to get all of various functionality in sync."
SAN management has been another area in which users would like improvement. "We have a mixed SAN environment and find it difficult to use one set of management tools to see how well all of our SAN equipment is functioning," said Ben Kobler, computer scientist at NASA's Goddard Space Flight Center. Vendors have been enhancing their management systems and crafting additional standards to ease maintenance chores.
The additional improvements should help keep the technology on the acceptance path. "We're quite bullish on Fibre Channel's future and expect it to be the primary method of moving large files on SANs for quite a few years," said Steve Duplessie, a senior analyst with the Enterprise Storage Group. n
Korzeniowski is a freelance writer in Sudbury, Mass., who specializes in technology issues. He can be reached at paulkorzen@ aol.com.
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