Storage Area Network Information Center

Building a Storage Area Network (SAN) prototype is often done from the center out, starting with the switches. Then, in an incremental and iterative manner, storage devices are added around the center of the SAN, followed by hosts. This approach will help you quickly locate and isolate problems. Once your prototype is working, you can run testing scenarios to ensure the SAN responds and recovers as expected.

Switches First, Edge Devices Second, Hosts Last

There are five key steps in building your prototype:

Step 1: Build your fabric. Connect each switch one by one and validate that each can see the other.

Step 2: Incrementally add and validate your edge storage devices, ensuring that each is visible to the switches.

Step 3: Add and validate your hosts incrementally, ensuring that each is visible to the switches.

Step 4: Validate that your hosts and storage devices can see each other.Validate that your hosts and storage devices can see each other.

Step 5: Once you've connected and validated visibility between your fabric, devices, and hosts, it's a best practice to disable your unused ports.

Create a Baseline Logical and Physical Diagram

A logical and physical diagram of your SAN is a helpful aid in testing and troubleshooting. A logical diagram illustrates the relationships between SAN components, such as zones, while a physical diagram includes the physical components of the SAN and how they are wired. These diagrams will provide a reference baseline during connectivity testing, and help set expectations for testing results.

Testing Scenarios

Creating failure scenarios like power cycling and resetting devices will help you discover marginal connections and malfunctioning equipment. Testing should include the fabric, hosts, and storage devices, all of which should recover gracefully from failures. The following should be tested:

• Failure scenarios
• Failover scenarios for dual fabrics
• Cable disconnect and reconnect scenarios
• Loss of inter-switch connectivity scenarios

After failures are injected, the fabric should be checked to ensure it reroutes traffic successfully and, once the failure has been corrected, re-establishes connectivity and reverts to normal routing.

Running an I/O Load

After failure scenario testing has been successfully completed, you can test performance by running an I/O load and analyzing the outcome. Using your planned application for load testing is optimal, however, this is often difficult if not impossible. If you cannot use your planned application, then you could use an I/O generator to run a simulated load. Operating systems manufacturers can provide recommendations on I/O generating tools.

Another option during I/O testing is to repeat your failure scenarios to see how they affect performance. Once all testing has been completed successfully, the time is right to transition your SAN into production.

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