VM becomes unresponsive with "Another task is already in progress" error during or after VM backup

Products

• VMware vSphere ESXi
• VMware vCenter Server

Issue/Introduction

• Virtual machines become unresponsive to all inputs during snapshot consolidation or deletion.
  
  
• Attempts to shut down the virtual machine or perform snapshot operations fail with the error message: "Another task is already in progress."


• This issue blocks administrative tasks and disrupts normal virtual machine operations.

Environment

• VMware vCenter Server 7.x
  
  
• VMware vCenter Server 8.x

Cause

Scheduled backups using 3rd party solutions create snapshots on the virtual machine that sometimes fail to delete upon completion. These snapshots grow significantly over time and cause task processing delays due to the size of the snapshot disk. A stale snapshot chain or an underlying task lock causes the virtual machine to become unresponsive, leading to timeouts in power operations or snapshot deletion.

Resolution

1. Refer to Powering off an unresponsive virtual machine on an ESXi host to identify and cancel the stuck task, releasing any backend locks on the virtual machine.
   
   
2. Restart the management agents on the ESXi host as described in Restarting Management Agents in ESXi to reset host-side services and clear stale states.
   
   
3. If the issue persists, migrate or shut down all virtual machines on the affected ESXi host excluding the affected VM, and then perform a COLD boot via iLO/DRAC to reset the host state fully and clear stale processes.
   
   
4. Exclude the virtual machine from the backup schedule to release the lock, then attempt to remove the snapshot.
   
   
5. If the issue persists, restore the virtual machine from a recent backup or clone the virtual machine.

Additional Information

For best practices regarding snapshot usage and cleanup, refer to Best practices for using VMware snapshots in the vSphere environment.