Using Host Diagnostic Tools - Cisco 9134 - MDS Multilayer Fabric Switch Troubleshooting Manual

Using Host Diagnostic Tools

S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m
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:
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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.
Cisco MDS 9000 Family Troubleshooting Guide, Release 3.x
B-28
Credit starvation
Missing, malformed, or non-standard-compliant frames or primitives
Protocol errors
Appendix B Troubleshooting Tools and Methodology
OL-9285-05