Error: vSphere HA cannot reset this virtual machine during snapshot consolidation

Products

• VMware vSphere ESXi

Issue/Introduction

Virtual machines experience unexpected restarts or "vSphere HA cannot reset this virtual machine" warning events. This typically occurs during backup activities, specifically during the snapshot removal or consolidation phase.

• The vSphere Client displays warnings: vSphere HA cannot reset this virtual machine.
• VMs reboot repeatedly during the backup window.
• vmware.log analysis shows snapshot stun durations exceeding 30–60 seconds.
• Average stun times observed around 8 seconds, with peaks over 100 seconds.

Environment

• VMware vSphere ESXi 7.x / 8.x
• VMware vCenter Server 7.x / 8.x
• Backup and Recovery software

Cause

This issue occurs when the snapshot consolidation process stuns the virtual machine for a duration that exceeds the vSphere HA monitoring failure interval. When the VM is stunned (unresponsive) for too long, HA interprets this as a failure and attempts to reset the VM. If the consolidation lock is still active, the reset may fail, leading to the "cannot reset" warning.

Resolution

1. Verify the vSphere HA cluster "VM Monitoring" settings. Increase the failure interval to exceed the maximum observed stun time if storage latency cannot be reduced.
2. Disable the Automatic Virtual Machine Startup and Shutdown feature on all hosts within the HA cluster. This feature is not supported and conflicts with HA.
3. Review storage performance and datastore latency during the backup window to reduce consolidation time.
4. Ensure VMware Tools is up to date on all affected VMs to optimize guest-level quiescing.
5. Contact backup vendor.

Additional Information

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