Solutions in this chapter:

• The Troubleshooting Approach: The SAN Is a Virtual Cable

• Troubleshooting the Fabric

• Troubleshooting Devices that Cannot Be Seen

• Troubleshooting Marginal Links

• Troubleshooting I/O Pauses

• Summary

• Solutions Fast Track

• Frequently Asked Questions

Introduction

A SAN is a complex system that can consist of multiple switches, hosts, storage devices, routers, and hubs. A SAN can also be as simple as a single switch with attached storage and hosts. A breakdown of the individual components yields a range of subcomponents, from simple subcomponents, such as cables, to complex subcomponents, such as switches. At a macro level, the fabric itself is considered a component that might require troubleshooting. Switches are logically positioned in the middle of the network between hosts and storage, and have visibility to both storage and hosts. This visibility into both sides of the storage network enables you to use switches to determine the cause of any malfunction in the SAN. This chapter presents a structured process for identifying marginal or faulty SAN components by helping you figure out where to start and then to methodically home in on the problem. Specific areas of focus include troubleshooting the following symptoms and SAN components:

• Fabric

• Missing devices

• Marginal links

• Input/Output (I/O) interruptions

The context of your problem influences how to interpret the data output by the variety of commands available in Fabric OS. For example, focus on the port state information for switchShow output when you are troubleshooting a port issue, and the switch status...