SAN centerpiece
Brocade sharpens performance, manageability on its 16-port switch
VARIOUS DEVICES PLAY vital roles in building a SAN (storage area network). Hubs and loop switches are the SAN entry point for legacy devices; fabric switches are the backbone of the network; and director-class switches combine the characteristics of multiple fabric switches to improve a unit’s resilience and capacity.
Fortunately, companies that want to reduce the cost of ever-increasing storage can choose from an array of quality switches from reputable vendors. But parallel factors, such as the slow economy and the promise of IP storage as a less expensive alternative to fiber SAN, have taken their toll on switch vendors’ revenues, triggering fierce competition.
Brocade is the undisputed, but not unchallenged, market leader with about 50 percent of the overall switch market revenue, according to IDC estimates for 2001. McData follows with a significant 32 percent share. Interestingly, according to the same report, Brocade dominates the fabric-switch segment with 84 percent of the revenues, whereas McData takes the lion’s share of the director-class switch with 77 percent, followed by Inrange with a 23 percent share.
Under pressure to maintain its lead, Brocade recently renovated its renowned SilkWorm fiber switch line, which features units varying in port numbers, speed, and size, adding support for 2Gbps and boosting management features.
We reviewed one of the latest additions to the line, the SilkWorm 3800. Boasting 16 ports that automatically adjust their speed to 1Gbps or 2Gbps, this fabric switch offers interesting features, including the ability of attaching loop devices, improved fabric configuration, and management functionality.
If you are considering building or expanding your SAN, the Brocade SilkWorm 3800 should be the first item on your shopping list because of its excellent flexibility, scalability, and performance. In addition, its management software makes adapting the storage network to different requirements easy.
A fabric switch such as the Brocade Silkworm 3800 is the centerpiece of a SAN. This intelligent piece of equipment can connect servers, storage devices, or other fiber switches to its 16 ports. Each 2Gbps port can sustain a full duplex transfer rate of 200MBps, which provides more than enough capacity for the average server, and adapts automatically to slower devices.
You could build a minimal SAN around a single SilkWorm switch connecting servers and storage devices such as disks or tapes, though it would lack resilience and would have limited scalability. But a single switch is obviously a single point of failure, and the concurrence of I/O intensive applications, such as backing up data or taking instant snapshots of a database, requires distributing the load on more paths. Hence, additional switches are a must.
That’s where the 3800’s exceptional adaptability comes in handy: By connecting multiple switches, you can design a network of devices with redundant connections that is shaped according to typical models, such as a mesh or a star configuration, and responds better to the business and applications requirements. For bulletproof resilience, server and storage devices can be connected to two independent fabrics, each able to sustain the data traffic.
We built our test SAN around two, 16-port Brocade Silkworm 3800 switches. We linked the two switches together using ISL (inter-switch link) cables on four ports. At one end we connected two Dell servers, each with an Emulex LightPulse 9000 HBA (host bus adapter), while running Windows 2000. The second switch connected two arrays of 16 Seagate 34GB fiber drives.
To complete our hardware settings, we linked each switch to our LAN and to the serial ports of our servers. We used these connections to configure our SAN. Using the serial connection and the 3800’s CLI (command line interface), we set the IP address for each switch, then we pointed our browser to that address to access the GUI of WebTools, the Brocade management software.
Out first task was to partition our fabric into two logical segments to restrict each server to a limited number of storage devices. Using WebTools, we quickly created separate zones, essentially restricting each server to a single 16-disk array. Our zoning was based on switch ports, however, the 3800 offers the option of using WWN (worldwide names, the unique identifier of a fiber device), or a combination of WWNs and ports — a good compromise of flexibility and security.
Our next task was to define trunking, probably the most interesting and performance-critical configuration activity for your SAN. We dedicated a group of four ports to carry data traffic between two switches. The resulting trunk was a wider pipe, capable of sustaining a transfer rate of up to 8Gbps.
Next, we put that wider pipe to the test. To simulate a load, we started Intel Iometer on each server, spreading I/O operation across the entire array. Then we started the WebTools performance-monitoring GUI.
The traffic generated by our two servers was no challenge for the 3800: It flowed smoothly across the trunk, spread evenly and automatically over each port. To mimic a fault condition, we disconnected one of the ISLs: Not a hiccup on the servers, and the data traffic evenly divided across three ports. Reconnecting the ISL brought the trunk back to full operation.
Singling out a winner among the Silkworm 3800’s capabilities is difficult. Trunking ranks high because it creates reliable, self-correcting paths among switches to keep your SAN humming.
We were impressed with the Brocade SilkWorm 3800 thanks to its first-class hardware capability and a set of management tools that helps configuration activities and performance monitoring on the whole fabric, not just a single switch. Whatever the size of your storage network, the Brocade 3800 is a must-have.
