SANs Go Wireless

The firm of Steinbach Credit Union, based in the predominantly Mennonite town of Steinbach, is one of the first reported companies to implement a wireless storage-area network (SAN). With the success of this project, Steinbach becomes an example of how customers are coming up with interesting solutions in the face of tight budgets. The company installed this SAN solution at a cost of about $600,000,and that's Canadian dollars. (That's roughly $417,000 in U.S. dollars.)

"This is a real unique and clever way to combine technology," says Tom Clark, director of technical marketing at Nishan Systems, one of the companies that helped build the system. "It is using wireless transmission for SAN traffic."

The solution involves two SANs separated miles from each other across the flat Canadian prairies, comprising equipment from Xiotech, Cisco and Nishan Systems (see "Solution Snapshot," left). But the most important key is the use of Proxim wireless Ethernet radios coupled with 100Base-T,also known as "Ethernet in the sky."

The system has been up since February. Transfer rates from one SAN to the other run at about 7 MBps when the system is doing a full remirroring image.

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"Let's say you were running a server, you had an eight-bit SCSI card in it, and you are doing internal mirroring. Your transfer rate would only be about 5 MBps," says Denis Van Dale, network administrator for Steinbach Credit Union. "We are doing this over 40 miles, which blows me away."

In a nutshell, Steinbach Credit Union has configured together two Fibre Channel SANs, one at the company's headquarters in Steinbach and the other in a new branch office in Winnipeg. In between these primary and secondary sites, the job of the Nishan switches is to convert Fibre Channel from the SANs to Gigabit Ethernet and IP, Clark says.

In turn, the Nishan devices hand off the job to a Cisco switch, which also links into the company's LAN system and is used to adjust the bandwidth from a high speed of 1,000 Mbps to a lower 100 Mbps. The Cisco switch then connects to the Proxim radio bridges that take the standard Ethernet and turns it into wireless Ethernet for transmission along three radio control towers. Spread 16 miles apart, the towers and the bridges function on a 5.8-GHz transmission.

Steinbach, who worked closely with Proxim engineers, along with Xiotech and Nishan representatives, feels the radio system has bulletproof security in transmitting data. For instance, the system uses a tightly focused beam, "so someone driving around with a handheld detector and computer would never get information," Van Dale says. "Over a distance of 16 miles, the beam is just a little bit larger than the dish it is aimed at."

Plus, the data is encrypted two to the 48th power, so the estimate is that if you try a different code every 5 seconds, it would take 1 million years to break the code, Van Dale says.

One of the most interesting points: The center tower had to be almost exactly dead center between the SAN locations for this solution to work. So engineers used a Global Position Survey to find the exact spot for the center tower. This was important because Steinbach Credit Union, which has more than 47,000 members and assets in excess of C$1 billion (US$683.4 million), needed to do data replication between two points over a 40-mile distance, and it needed to do so relatively cheaply. It could have leased dark fibre from the Manitoba telephone system, but that would have cost nearly $70,000 ($48,000 USD) per month. The company also could have laid out the dark fibre itself, but that would probably have run into at least $1 million.

"We didn't even get an estimate because we can't even think of affording that," Van Dale says.

One factor to consider when implementing such a solution is fault tolerance. Van Dale says Proxim has promised Steinbach "five nines" (99.999 percent) reliability. The systems aren't affected by weather because of the bandwidth used. "It's not bothered by rain, snow or fog. It would take a direct hit on the center tower to take it down," Van Dale says. "It's not like a satellite system where if it rains really hard, your TV disappears."