Troubleshooting ESXi Host SAN/Network Performance Issues: A Step-By-Step Guide with Sample Error Messages and Expected Values
Introduction:
Degraded performance in virtualized environments can have a significant impact on business operations. In this blog post, we will walk through a real-world scenario where an organization experienced performance issues, and how they successfully diagnosed and resolved the problem. The issue started with noticing degraded performance across all systems, which led to checking the SAN, finding nothing wrong, and eventually examining ESXi logs. This step-by-step guide will cover how to identify and resolve network performance issues in ESXi environments, focusing on fiber connections and SFPs, and providing sample error messages and correct expected values.
Identifying the Issue:
In our scenario, the first clue was found in the vmkwarning.log on the ESXi hosts, where the following error message appeared: "state in doubt; requested fast path state update." This message suggested that there might be a communication issue between the ESXi hosts and the storage array.
Sample error message: "2023-04-26T09:32:15Z cpu3:2097242)WARNING: NMP: nmp_DeviceRequestFastDeviceProbe:237: NMP device "naa.5006016341e01555" state in doubt; requested fast path state update..."
Checking the Fiber Switch:
Upon investigating the fiber switch, frame drops were noticed on the ports corresponding to the ESXi hosts exhibiting the error message. Additionally, CRC errors were observed, indicating potential issues with the network connectivity or SFPs.
Sample error message: "Port 5: Rx CRC error counter: 150"
Inspecting the SFPs on the Fiber Switch:
The SFPs on the fiber switch were inspected for correct specifications, such as speed, wavelength, type, fiber mode, and distance rating. Some SFPs with values out of range were replaced, and the majority of the errors were resolved. However, a few connections still exhibited issues.
Correct expected values (example): Speed - 10Gbps, Wavelength - 850nm (multimode fiber), Type - SFP+, Fiber mode - MMF (multimode fiber), Distance rating - 300 meters
Inspecting the SFPs on the Server/Host Side:
After addressing the SFPs on the fiber switch side, attention was turned to the server/host side. The SFPs on the server/host side were inspected and compared to the switch-side SFP specifications. Any discrepancies or damaged SFPs were replaced, and the fiber connectors were cleaned.
Correct expected values (example): Speed - 10Gbps, Wavelength - 850nm (multimode fiber), Type - SFP+, Fiber mode - MMF (multimode fiber), Distance rating - 300 meters
Monitoring the Connections:
Following the replacement of the SFPs on the server/host side, the connections were monitored for improvements in CRC errors, dropped frames, and overall performance. In our scenario, the remaining issues were resolved, and system performance returned to normal.
Sample improvement: "Port 5: Rx CRC error counter: 0"
Conclusion:
In this blog post, we have provided a step-by-step guide to diagnosing and resolving network performance issues in ESXi environments, complete with sample error messages and correct expected values. By systematically investigating the fiber switch, SFPs, and network connections, it is possible to identify and resolve problems that may be affecting system performance. This approach can help IT administrators maintain optimal performance in their virtualized environments and ensure smooth business operations.
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