VDDK restores thin-provisioned disk of a virtual machine residing on NFS as thick-provisioned disk

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms:

• You are unable to restore a thin-provisioned disk on NFS using the Virtual Disk Development Kit (VDDK).
• The QueryChangedDiskAreas("*") API returns the error:
  
  Msg:'SOAP 1.1 fault: "":ServerFaultCode [no subcode]
  "Error caused by file /vmfs/volumes/6c0378da-9f01ff6c/VMName/VMName.vmdk"

Environment

VMware Virtual Disk Development 1.2
Virtual Disk Development Kit 5.0
Virtual Disk Development Kit 5.1
Virtual Disk Development Kit 5.5
Virtual Disk Development Kit 6.0

Cause

This issue occurs because Changed Block Tracking (CBT) is not supported when the ChangeID is set to "*" against virtual machines residing on NFS. The QueryChangedDiskAreas("*") API returns an error against NFS version 3 and earlier.

Note: vSphere 6.0 supports NFS version 4, which provides sector change information, however NFSv4 does not provide the FIEMAP ioctl, so CBT still cannot be used to query changed sectors for backup and restore operations.

Resolution

This is expected behavior. CBT with a change ID equal to "*" is supported only on VMFS file systems.

To work around this issue, migrate thin-provisioned virtual machines from an NFS datastore to a VMFS datastore for thin-provisoned disk backup or restore operations.

Additional Information

For related information, see:

• Changed Block Tracking (CBT) on virtual machines (1020128)
• Changed Block Tracking on Virtual Disks in the VMware Virtual Disk Programming Guide for VDDK 5.5.

Changed Block Tracking (CBT) on virtual machines