MSDN Documentation

Connectivity Issues

Problems with network connectivity can prevent you from accessing your VM.

Common Symptoms:

• Unable to RDP or SSH into the VM.
• Applications running on the VM cannot reach external resources or other VMs.
• VM status shows as "Not Responding" in the Azure portal.

Troubleshooting Steps:

1. Check Network Security Groups (NSGs): Ensure that NSGs associated with the VM's network interface or subnet allow inbound traffic on the appropriate ports (e.g., RDP 3389, SSH 22).
2. Verify Public IP Address: Confirm the VM has a public IP address assigned and that it's correctly configured for external access.
3. Examine Azure Firewall/UDRs: If you are using Azure Firewall or User Defined Routes (UDRs), verify their configurations are not blocking traffic.
4. VM Boot Diagnostics: Use the Boot Diagnostics feature in the Azure portal to view the VM's console output for clues about network configuration errors.
5. Connection Troubleshoot Tool: Utilize the Connection Troubleshoot tool in the Azure portal for network path analysis.

Remember to apply changes to NSGs and firewall rules carefully, as incorrect configurations can lead to broader connectivity loss.

Performance Degradation

Slow VM performance can be caused by a variety of factors, including resource constraints or misconfigurations.

Common Symptoms:

• High CPU utilization (consistently above 80-90%).
• Low disk I/O performance or high disk latency.
• Slow application response times.
• VM becomes unresponsive.

Troubleshooting Steps:

1. Monitor Resource Utilization: Use Azure Monitor metrics (CPU, Memory, Disk IOPS, Disk Throughput, Network In/Out) to identify resource bottlenecks.
2. Check Running Processes: Log in to the VM and use Task Manager (Windows) or top/htop (Linux) to identify processes consuming excessive CPU or memory.
3. Review VM Size: Ensure the VM size chosen meets the workload requirements. Consider resizing the VM to a larger or more appropriate SKU.
4. Disk Performance: Verify that the disk type (Standard HDD, Standard SSD, Premium SSD) is appropriate for the workload's I/O needs. Check disk cache settings.
5. Background Tasks: Identify and optimize any background tasks, updates, or antivirus scans that might be impacting performance.

Consider using Azure Advisor recommendations for performance optimization insights.

Application Failures

Applications running on VMs may encounter errors or fail to start.

Common Symptoms:

• Application crashes or stops responding.
• Error messages related to dependencies, libraries, or configuration.
• Services fail to start or run.

Troubleshooting Steps:

1. Review Application Logs: Examine application-specific log files for error messages and stack traces.
2. Check Event Viewer/System Logs: On Windows, check the Event Viewer (Application and System logs). On Linux, examine logs in /var/log.
3. Verify Dependencies: Ensure all required libraries, frameworks, and services are installed and configured correctly on the VM.
4. Run Application Diagnostics: If the application has built-in diagnostic tools, use them to identify issues.
5. Test with Minimal Configuration: Try running the application with a simplified configuration or with fewer dependencies to isolate the problem.

Disk and Storage Issues

Problems with VM disks can lead to data loss, performance issues, or inability to boot.

Common Symptoms:

• VM fails to start due to missing or corrupted OS disk.
• Data disks are not accessible or show errors.
• Disk I/O errors in logs.

Troubleshooting Steps:

1. Check Disk Attached Status: Verify in the Azure portal that the disks are correctly attached to the VM.
2. Use Disk Management/fdisk: Log in to the VM and use disk management tools to check disk partitions and file system integrity.
3. Re-attach Disk: As a troubleshooting step, try detaching and re-attaching the problematic disk.
4. Snapshot and Restore: If data corruption is suspected, take a snapshot of the disk and attempt to restore from it.
5. Disk Encryption Issues: If using Azure Disk Encryption, ensure the key vault and permissions are correctly configured.