Troubleshooting Common SAN Fibre Channel Errors

Diagnosing and Troubleshooting Common SAN Fabric Errors

SAN Fibre (or Fabric) Errors Issues can really cause a lot of headaches for the configuration and performance of your SAN infrastructure. Here’s a look at some of the most common SAN Fabric errors and their potential fixes.

Common Error 1: Invalid Ordered Set Flow Control

Invalid ordered sets essentially have to deal with flow control, and you can get these under a few different conditions.

The first condition especially happens with older microcode. This is where you get into a Fill-Word situation where the fill word is not set correctly. This was the case in Figure 1 below. We can see that at around 4:00 PM the errors completely dropped.

Figure 1: Invalid Ordered Sets

This occurred because the fill words were fixed on the switches that were having the problem.

Common Error 2: Invalid Ordered Media Issues

Another issue that can occur regarding invalid ordered sets or invalid transmission words may be issues with your media, which may be your GBIC’s or your fiber optic cables. To avoid these common SAN Fabric issues, you want to make sure those are tight, clean, and undamaged.

Figure 2 below shows the Cycle Redundancy Check (CDC) Errors.

Figure 2: Cyclic Redundancy Check (CDC) Errors

We can see that the errors happened between 10:15 AM and 3:15 PM. These definitely indicate a problem with the media. This is an encoding error and it means that the frames are being marked invalid because of some problem along the data path.

A roundup of the other Common Physical Media Errors include:

• Discards
• CRC’s when there are timeouts
• Frame issues
• Transmission order issues

You’ll also see link failures and signal failures when you have issues where a host bus adapter resets, or a cable is unplugged or receded.

Common Error 3: Buffer Credit Issues

Buffer credit issues are issues where you don’t have enough buffers to transmit or receive data and those actions are made to wait until there’s enough buffer credit available. We tend not to dive into these issues unless there are significant numbers.

Figure 3: Zero Buffer to Buffer Credits

Resolve Common SAN Fibre Channel Issues with Built-in AI

Watch the full video above for a detailed walk-through of these common SAN Fibre Channel issues.

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