Error: ToolsBackup: not enough empty nodes - VSS writers missing causing backup failures

Products

• VMware vSphere ESXi

Issue/Introduction

When you take a snapshot with quiesce guest file system enabled, your application-aware backups fail. Volume Shadow Copy Service (VSS) writer XML files are missing from the vss_manifest.zip file. You see this error in vmware.log:

ToolsBackup: not enough empty nodes (needed X, found Y)

This occurs on virtual machines with 8 or more disks on a single SCSI controller. Your backup software cannot complete application-consistent backups.

Common customer problem descriptions:

• "Snapshot with Quiesce guest files issue"
• "Snapshot does not include writer.xml files causing our snapshot based application aware backups to fail"
• "writer.xml files are not created during backup"
• "When a snapshot is created a manifest????.zip with xml for all the Windows VSS writers should be created... but there are no xml files in the manifest.zip"
• "VM backup is getting failed and we noticed that the writer xml files are missing from snapshot file"
• "VM backup failing for one particular VM in the environment"
• "The following files created when creating a snapshot do not include writers.xml"
• "Manifests file does not generate writer.xml files"
• "While taking quiesce snapshot, writer.xml files are not generating
• "Intellisnap (App aware) backups are not completing for the VM's"

Environment

Seen in:

• VMware vSphere 7.0
• VMware vSphere 8.0

Cause

VMware's snapshot quiesce mechanism temporarily hot-adds snapshot disks during VSS operations. Each disk needs one available SCSI slot. A single SCSI controller supports 15 devices maximum (14 usable slots).

When your VM has 8+ disks and insufficient free slots remain, the hot-add operation fails. This prevents the VSS enumeration process from completing. Without successful enumeration, no individual VSS writer XML files are created in the vss_manifest.zip file.

Resolution

1. Power off the affected virtual machine.
2. Log in to the vSphere Client.
3. Right-click the virtual machine and select Edit Settings.
4. Click Add New Device and select SCSI Controller.
5. Select the controller type (LSI Logic SAS recommended).
6. Click OK to save changes.
7. Power on the virtual machine.
8. Verify the new controller in Windows Device Manager.
9. Take a test snapshot with Quiesce guest file system enabled.
10. Verify individual writer XML files exist in vss_manifest.zip.

Note: Contact Broadcom Support before changing Raw Device Mapping (RDM) configurations.

Additional Information

For more information, see Troubleshooting Volume Shadow Copy (VSS) quiesce related issues.

Understanding VSS Writer Files

When VSS quiesce succeeds, the vss_manifest.zip contains individual XML files for each Windows VSS writer: • System Writer-{GUID}.xml • SqlServerWriter-{GUID}.xml • Registry Writer-{GUID}.xml • Additional writer files based on installed applications

When this issue occurs, the manifest file exists but contains no writer XML files.

Best Practices

• Use multiple SCSI controllers for VMs with 8+ disks • Keep 2-3 empty slots per controller • Maximum 4 SCSI controllers per VM (56 total disk slots)

Prevention

Monitor vmware.log during backups. The "not enough empty nodes" error indicates controller capacity issues before failures occur.