Cisco DS-C9124-K9 Troubleshooting Guide - Page 544
Fibre Channel Testers, Fibre Channel Protocol Analyzers, Using Host Diagnostic Tools
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Using Host Diagnostic Tools Appendix B Troubleshooting Tools and Methodology Send documentation comments to [email protected] Fibre Channel Testers Fibre Channel testers are generally used to troubleshoot low-level protocol functions (such as Link Initialization). Usually these devices operate at 1- or 2-Gbps and provide the capability to create customized low-level Fibre Channel primitive sequences. Fibre Channel testers are primarily used to ensure physical connectivity and low-level protocol compatibility, such as with different operative modes like Point-to-Point or Loop mode. Fibre Channel testers and more generalized optical testers may used to spot broken cables, speed mismatch, link initialization problems and transmission errors. These devices sometimes incorporate higher-level protocol analysis tools and may bundled with generic protocol analyzers. Fibre Channel Protocol Analyzers An external protocol analyzer (for example from Finisar), is capable of capturing and decoding link level issues and the fibre channel ordered sets which comprise the fibre channel frame. The Cisco MDS 9000 Family Port Analyzer Adapter, does not capture and decode at the ordered set level. A Fibre Channel protocol analyzer captures transmitted information from the physical layer of the Fibre Channel network. Because these devices are physically located on the network instead of at a software re-assembly layer like most Ethernet analyzers, Fibre Channel protocol analyzers can monitor data from the 8b/10b level all the way to the embedded upper-layer protocols. Fibre Channel network devices (HBAs, switches, and storage subsystems) are not able to monitor many SAN behavior patterns. Also, management tools that gather data from these devices are not necessarily aware of problems occurring at the Fibre Channel physical, framing, or SCSI upper layers for a number of reasons. Fibre Channel devices are specialized for handling and distributing incoming and outgoing data streams. When devices are under maximum loads, which is when problems often occur, the device resources available for error reporting are typically at a minimum and are frequently inadequate for accurate error tracking. Also, Fibre Channel host bus adapters (HBAs) do not provide the ability to capture raw network data. For these reasons, a protocol analyzer may be more important in troubleshooting a storage network than in a typical Ethernet network. There are a number of common SAN problems that occur in deployed systems and test environments that are visible only with a Fibre Channel analyzer. These include the following: • Credit starvation • Missing, malformed, or non-standard-compliant frames or primitives • Protocol errors Using Host Diagnostic Tools Most host systems provide utilities or other tools that you can use for troubleshooting the connection to the allocated storage. For example, on a Windows system, you can use the Diskmon or Disk Management tool to verify accessibility of the storage and to perform some basic monitoring and administrative tasks on the visible volumes. B-28 Cisco MDS 9000 Family Troubleshooting Guide, Release 3.x OL-9285-05