Extending a virtual disk fails with the error:msg.disklib.UNSUPPORTEDFEATURE

Products

• VMware vSphere ESXi

Issue/Introduction

This article provides steps to edit the descriptor file (vm.vmdk) of the failing base disk and modify the PID to ffffffff.

Symptoms:

• Extending a virtual disk fails.
• The VMware vSphere Client displays the error:
  
  Hot-extend is currently supported only for VMFS flat virtual disks without snapshots opened in persistent mode.
  The disk extend operation failed: msg.disklib.UNSUPPORTEDFEATURE
• In the /vmfs/volumes/VM_Directory/vmware.log file of the affected virtual machine, there are entries similar to:
  
  <YYYY-MM-DD>T<time> 015Z| vmx| I120: HotExtend: Extending scsi1:0 to 167772160
  <YYYY-MM-DD>T<time> 025Z| vmx| I120: Msg_Post: Error
  <YYYY-MM-DD>T<time> 025Z| vmx| I120: [msg.disk.hotextend.Failed] Failed to extend disk scsi1:0.
  
  </time></time></time>
  
  Note: The preceding log excerpts are only examples. Date, time, and environmental variables may vary depending on your environment. 　
   
• Extending the virtual disk fails regardless of the virtual machine's power state.

Environment

• VMware vSphere ESXi 7.0.x
• VMware vSphere ESXi 8.0.x
  
  

Cause

This issue occurs when the ParentCID of the base disk is not set to ffffffff.

For example:

 

# Disk DescriptorFile

version=3

encoding="UTF-8"

CID=27eaf453

parentCID=72ca12de

isNativeSnapshot="no"

createType="vmfs"

Resolution

To resolve this issue, edit the descriptor file (vm.vmdk) of the failing base disk and modify the PID to ffffffff.

To edit the descriptor (vm.vmdk) file:

Note: Ensure to take a backup of the virtual machine before proceeding with these steps.

1. Log in as root to the ESXi host through SSH.
2. Modify the descriptor (vm.vmdk) file by running this command:
   
   vi /vmfs/volumes/datastore/VM_Directory/vm.vmdk
   
   For more information, see Editing files on an ESX host using vi or nano (1020302).
   
   For example:
   
   # Disk DescriptorFile
   version=3
   encoding="UTF-8"
   CID=27eaf453
   parentCID=ffffffff
   isNativeSnapshot="no"
   createType="vmfs"
    
3. Save and close the file.

Additional Information

Recreating a missing virtual machine disk descriptor file