Wager on iSCSI SAN Pays Off

Wireless Retail installs Cisco's SN 5428 router at system's core.

Last spring, Wireless Retail faced a problem that is all too common with todays networks: Data was growing at a rate faster than the companys direct-attached storage could support. The solution? A SAN that bets on the performance and management promise of iSCSI.

After deciding that a block-level storage system would best fit its data storage and access requirements—including database data and e-mail—the wireless voice and data product retailers final decision was between the industry-standard Fibre Channel and newcomer iSCSI.

Wireless Retail uses mostly rack-dense, two-way servers, each costing roughly $2,500. Based on the bids it received from VARs, a Fibre Channel storage area network would have more than doubled Wireless Retails overall hardware cost when the extra expense of Fibre Channel switches was figured in. This made no economic sense for the midsize Wireless Retail, whose total employees number about 3,500 nationwide.

"Based on the average of the quotes we received upfront from EMC [Corp.] and two VARs, we saved roughly $1,500 per Fibre Channel [host bus adapter by going with iSCSI]," said Wireless Retail IT Director George Nathanson, in Scottsdale, Ariz.

If it had gone the Fibre Channel route, said Nathanson, Wireless Retail would also have had to shell out money for software licenses—totaling about $1,000 per card—for multipathing support, something already built into the companys IP network.

In the end, Wireless Retail chose to go with Cisco Systems Inc.s new Cisco SN 5428 Storage Router (click here to see a review of the router) as the core of its iSCSI SAN instead of a Fibre Channel SAN based on Brocade Communications Systems Inc. technology.

Although economics was important in Wireless Retails decision, it wasnt the only factor. Nathanson said the fact that iSCSI not only leverages IP networking infrastructure but also IP networking skills was important in making the decision. "We had nobody with experience in Fibre, and we didnt want to rely on consultants," he said.

In the rollout, Wireless Retail is using its iSCSI-based SAN to provide storage services for five major servers: two file servers, servers running Exchange and SQL Server, and a digital imaging server.

One application notable for its absence from the SAN is Wireless Retails point-of-sale SQL database, which has strict performance guidelines and currently resides on a direct-attached storage system. The reason for its absence highlights the fact that iSCSI-based SANs cant compete with Fibre Channel-based SANs and direct-attached storage when it comes to performance. Only when iSCSI devices get faster will it make sense to store transaction-intensive applications on iSCSI-based networks.

A Cisco iSCSI driver is installed on each of the Wireless Retail servers serviced by the SAN, and from there, the servers are hooked into twin Cisco SN 5428 Storage Routers set in high- availability mode. (Each server is equipped with twin Gigabit Ethernet adapters for redundancy.)

As a closer look at Wireless Retails network topology reveals, IP networking dominates the links to the initiators (servers and clients that use the storage), but the connection to the targets (storage systems) is still Fibre Channel-based.

There are currently no native iSCSI RAID or disk storage units on the market, a void that grew wider when IBM pulled its iSCSI-based RAID off the market. As a result, storage routers such as Ciscos will be essential for bridging the gap.

Wireless Retail has also consolidated storage onto a 1-terabyte Hewlett-Packard Co. Compaq StorageWorks Modular Array 8000, and plans are in place to grow this unit to 2 terabytes as the company continues to accumulate data.

Storage consolidation is an important goal for Wireless Retail. "[The iSCSI-based SAN] works great for projects we have coming now," said Nathanson. "The imaging project is a storage hog we needed to get on a SAN, and we would much rather buy disks for a SAN than for individual servers."

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