Storage Area Network Information Center

Monitoring tools will alert you to problems in your Storage Area Network (SAN), and should provide you with some information to help troubleshoot your problem. If a problem arises, use an iterative approach starting at the center of your SAN to further diagnose where the problem lies.

Start Troubleshooting From the Center Out

Begin troubleshooting at the center of your SAN - the fabric. Because switches are located between your hosts and storage devices, and have visibility into both sides of the storage network, starting with them can help divide your search path in half. After eliminating the possibility of a fault within the fabric, you should then be able to see if the problem is on the storage side or the host side, and continue a more detailed diagnosis from there. By using this approach you can quickly pinpoint and isolate problems.

For example, if a host cannot see a storage device, you can run a simple switch command to see if the storage device is logically connected to the switch. If not, you know to focus first on the storage side. Use storage diagnostic tools to better understand why it is not visible to the switch. Once you can see the storage from the switch, if the host still cannot see the storage device, then you know there is still a problem between the host and switch. Run a switch command to see if the host is logically connected to the switch. If not, then host diagnostics will help you better understand why it is not visible to the switch.

Troubleshooting Focus Areas

• Missing devices
• Marginal links (unstable connections)
• Incorrect zoning configurations
• Incorrect switch configurations

• Physical issues between switch and devices
• Incorrect storage software configurations

• Incorrect host bus adapter installation
• Incorrect device driver installation
• Incorrect device driver configuration

• Incorrect installation and configuration of the storage devices that the software references. For example, if using a volume-management application, check for:
  • Incorrect volume installation
  • Incorrect volume configuration

Tools to Aid In Your Troubleshooting

There are many tools available to help you troubleshoot your SAN:

• Switch LEDs
• Switch commands for diagnostics (command line)
• Web or GUI-based monitoring and management software tools
• Real-time distributed fabric operating system with advanced diagnostics

• Device LEDs
• Storage diagnostic tools

• Host adaptor LEDs
• Host operating system diagnostic tools
• Device driver diagnostic tools

• Application-specific tools and resources

Contact Your SAN Support Vendor

If you can't solve a problem using the techniques and tools described above, your support vendor may be able to help. Write a general description of the problem and as much supporting detail as possible before you call. Your vendor product manuals may include worksheets that outline the information you should gather before you call, or you can create your own support worksheet (DOC) using this template.

With a basic understanding of SANs, you'll be able to solve all but the most complex issues yourself. The redundancy and re-routing features in your SAN will keep your operations running, giving you ample time to troubleshoot and resolve problems, or to gain assistance from your SAN support vendor(s).

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