Why did my Azure VM restart unexpectedly?

Question

Note: Based on common issues that we have seen from customers and other sources, we are posting these questions to help the Azure community.

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Why did my server get redeployed and my Azure Virtual Machine (running SAP) restart unexpectedly? How do I investigate the restart?

Answer 1

Note: Based on common issues that we have seen from customers and other sources, we are posting these questions to help the Azure community.

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Why did my VM reboot unexpectedly?

There are a number of reasons why your VM might reboot. One common cause is planned maintenance where Azure periodically updates its platform to improve the reliability, performance, and security of the host infrastructure for virtual machines. You can minimize the impact of planned maintenance by utilizing self-service maintenance, high availability, and other tools that are available:

https://learn.microsoft.com/en-us/azure/virtual-machines/maintenance-configurations

Detailed list of possible VM restart causes and how to get more information

There are a number of possible causes for an unexpected VM reboot and the documentation covers troubleshooting in more detail:

Understand a system reboot for Azure VM

Getting more information:

• Check resource health information: Azure Resource Health is a service that exposes the health of individual Azure resources and provides actionable guidance for troubleshooting problems.
• Check the activity log: Resource Health alerts are sent based on the activity Log information. Note that VM downtimes won't show in the activity log when a VM is created or migrated to a new host, if the VM availability state changes from Available to Unavailable and back within 35 seconds, or if the VM health changes from a state to Unknown and back to the original state as this is filtered out.
• Check the Azure Service Health Dashboard (link ) to see if something has affected VMs in your datacenter (rare).
• Diagnose VM restarts using the Diagnose and Solve blade on the VM blade to run additional diagnostics.

Causes - Maintenance:

• Planned maintenance sometimes requires a reboot. You can read more about planned maintenance for VMs as well as how to schedule planned maintenance.
• Memory-preserving updates should not have an impact on users however the VM will enter the paused state and then be resumed typically within 30 seconds.
• User-initiated reboot/shutdown is in the activity log if it is initiated from Azure and in the system logs if it's initiated in the OS.
• Microsoft Defender for Cloud and Windows will apply updates as configured.

Causes - Infrastructure:

• Host server faults can cause a reboot as the host server attempts a recovery (usually caused by hardware failure).
• Auto-recovery is rare but needed if a faulty host needs to be taken out of rotation and the VMs are automatically relocated to a different, healthy host server.
• VM crashes can be caused by the VM itself if the workload or role triggers a bug check.
• Storage-related forced shutdowns will happen if the availability or connectivity is affected for more than 120 seconds.
• Contact support by creating a support request if you've gone through everything and still are unable to determine why the VM is restarting.

Additional Reading:

• Understand a system reboot for Azure VM
• Troubleshoot unexpected reboots of VMs with attached VHDs
• OS start-up – Computer restarted unexpectedly or encountered an unexpected error
• Windows reboot loop on an Azure VM
• Azure Windows VM shutdown is stuck on "Restarting", "Shutting Down", or "Stopping services"