Quick Custom Optical Networks

DN Staff

April 10, 2006

3 Min Read
Quick Custom Optical Networks

Project description

Qlogic (Aliso Viejo, CA, www.qlogic.com) manufactures host-bus adapter cards that connect servers to storage devices and storage-area networks (SANs). Each time the company makes a design change, its test engineers must check performance, features and error handling.

Host adapters connect to storage devices and SANs over Fibre Channel links at data rates up to 4 Gbps or over Ethernet at 1 Gbps. To configure a test SAN, test engineers had to manually connect fiber-optic cables from the device under test to networks and test equipment. Whenever an engineer needed to test for a lost optical link, he or she had to manually disconnect and reconnect the optical cables. To increase productivity, staff engineer Matt Holley designed a configurable network using software-controlled physical-layer switches.

Holley designed a two-tiered switched optical network using a core switch/edge switch topology. The figure shows a simplified diagram of the network, which consists of 12, 144-port optical switches, 130 hosts, 42 Fibre Channel switches, 58 storage devices, six tape devices, three Fibre Channel analyzers and two Fibre Channel error generators in two labs. By the end of 2006, Holley plans to double the number of ports in the network from its current 1728 to more than 3400.

Ethernet connects the optical switches to a server running the configuration software. Engineers operate the configuration software over the company network, and the software schedules each use of the test system to avoid conflicts. Engineers can also invoke scripts that connect to the server to automate the test network's configuration.

During a test, the engineers introduce faults to verify that a host adapter recovers from errors. The error generators let engineers intercept and modify bits within frames or packets. They also break connections through the optical switches.

"If a connection is reestablished within 30 sec, then the host adapter should continue to work normally," said Holley. "We also test for broken connections that go longer than 30 sec. The connection should fail, but the host adapter should fail gracefully, without causing problems such as system crashes." Engineers verify that the host adapter can correct recoverable errors and provide error-free transmission.

After test engineers verify that a new product or updated product passes its tests, QLogic sends test results to Microsoft for device-driver certification. The company also sends test results to other software companies such as Red Hat and Novell for certification.

Lessons learned

Although the optical switches can connect network devices in seconds as opposed to 15 minutes per test, Holley found the test engineers were somewhat reluctant to move to an automated network. The optical switches more than doubled the number of cables and transceivers interconnecting devices, which confused some test engineers because they didn't know the exact cables they were using. If a manually-connected cable failed, they knew which one to replace. "We needed to train the test engineers on how the optical switches connect devices in the background," noted Holley.

For more on optical networks and to submit your own ideas, join our forum at: http://rbi.ims.ca/4919-522.

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