After completing a VM backup, the virtual machine fails to power on

Products

• VMware vSphere ESXi

Issue/Introduction

Post-backup, the virtual machine failed to power on. The following error was observed:
"File system specific implementation of OpenFile[file] failed. Failed to start the virtual machine. Module Disk power on failed. Cannot open the disk '/vmfs/volumes/XXXXXX-XXXXX-XXX-XXXXXX/XXXXXX/XXXXXXX_4.vmdk' or one of the snapshot disks it depends on. Failed to lock the file."

1. The VM is confirmed to be powered off, but failed to power on due to a lock on the XXXXXXX_4.vmdk file.
2. No snapshots are present that require consolidation.
3. Running lsof | grep -i <vmname>  revealed an active process still holding a lock.

Cause

The backup proxy VM locked the .vmdk file.
This issue can occur if a backup operation is interrupted or fails to complete cleanly. In such cases, the virtual machine’s .vmdk files may remain attached to the backup proxy VM, retaining the lock and preventing the original VM from powering on.

Resolution

1. Navigate to the backup proxy VM via the vCenter server UI.

2. Edit VM settings:
    Right-click the VM > Edit Settings

3. Inspect all attached Hard Disks:
     Expand each disk and look for references to the affected VM.

4. Detach the locked disk(s) associated with the impacted VM:
    Click the ‘X’ next to the associated disk(s).
    Important: Ensure not to select “Delete files from datastore.”

5. Retry powering on the impacted VM.

Note: Ensure no active backup is running while changes are being made.