SAN switching: Bigger is better

Looking to ensure resource availability and reduce the number of hops in storage-area networks, many users are opting for ever-bigger storage switches.

These director-level switches are high-port count, high-availability boxes that connect servers, storage and other fixed-port Fibre Channel switches to create a SAN. Many customers have chosen director-level switches - to build their SANs. According to IDC, revenue from the sale of director-level switches exceeded US$265 million in 2002.

Chassis-based switches comprise two categories: port-dense switches that have at least 64 ports; and director-level switches, which have at least 64 ports but also have high-availability features. Chassis-based switch vendors include Brocade, Cisco, CNT (formerly InRange), McData and QLogic. Cisco, CNT and McData also make director-level switches.

"Customers put in chassis-mounted switches for high availability for the most part and for increased port density," says Eric Sheppard, a senior analyst with IDC. Most chassis-based switches have a minimum capacity of 64 ports that are contained in an enclosure to which additional ports can be added.

"High availability means when you have a port or component failure in the chassis, the director can reassign and redirect traffic to different ports to avoid any disruption," says Jamie Gruener, a senior analyst with The Yankee Group. "That takes redundant fans and other components."

When Denis Krupennikov, director of IT for Oracle, was consolidating more than 40 data centers in his organization into three data centers in Redwood Shores, Calif.; Austin, Texas; and Colorado Springs, he chose McData director-level switches for their availability.

Bring down the SAN box

"Before we put in the SAN, every time we had to make a configuration change on an EMC (storage system) we had to take the box and applications down," Krupennikov says. "Adding in an EMC tower to the network before would require significant downtime for the host - connecting cables, etc. will take 10 to 12 hours at a minimum."

Krupennikov has 27 EMC Symmetrix storage systems and more than 700 Fibre Channel ports. As his network grows, Krupennikov will be able to add additional EMC Symmetrix systems without disruption.

"We needed to have something more flexible to reduce the downtime we have on our production ERP network. We decided to introduce director-level switches (from McData) between storage and hosts, and do the storage allocation and integration on the SAN level," Krupennikov says.

Gruener says other features of director-level switches make them ripe for adoption. "Several characteristics, such as performance and needing support for (Fibre Connection), drive the adoption of director-level switches, as well as consolidating how you manage the fabric as a whole," Gruener says. Fibre Connection lets users attach their SANs to IBM mainframe computers.

Managing a consolidated storage network was top priority for Peter Kahlenberg, vice president of DWS Investments, a subsidiary of Deutsche Bank Gruppe in Frankfurt, Germany.

Kahlenberg installed his SAN in 2001 "with the thought of consolidating different data centers into one big data center," he says.

He chose four 64-port CNT FC/9000 Fibre Channel/FICON Directors to consolidate "storage from different platforms like Novell, Windows NT, Windows 2000 and AIX, and to save administrators work because we have only one platform where we can administer our storage and our back-up device."

In each data center, Kahlenberg placed two FC/9000s for redundancy - each site replicates data over 1.8 miles to the other data center for business-continuity purposes.

He expects to grow his SAN without compromising on his plan to use director-level switches.

"We've never used smaller switches, because of the problem that you have to connect smaller switches to other switches for switch-to-switch communication and that's where you lose a lot of interconnect ports, so the availability of that is really bad," Kahlenberg says.

"If you have a lot of inter-switch links separating servers and storage, there is always latency bringing data from the server to the storage," he says.

What's the future of director-level switches?

It's a changing market now that Cisco is shipping Fibre Channel switches, analysts say.

In 2002, IDC says McData led the chassis-based market with a 55.8 percent market share, followed by Brocade with 29.2 percent and CNT with 15 percent.

These figures don't count for Cisco and QLogic, which each shipped 64-port or greater Fibre Channel switches this year.

Analysts say Cisco is going to gain ground quickly in this market.

Gruener expects Cisco to gain 12 percent to 15 percent of the Fibre Channel switch market by year-end. Cisco itself is no less humble in its aspirations - its CEO John Chambers says the company will be No. 1 or 2 in SANs.

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