Changing virtual disk provisioning from thick to thin requires moving the virtual disk to a different datastore. If the source and destination datastores are the same, vSphere performs no provisioning conversion.
To change the provisioning of a virtual machine base disk using Storage vMotion:
- Right-click the virtual machine and select Migrate
- Select Change storage only.
- In the Select storage page, select Configure per disk.
- Locate the virtual disk you wish to conver.
- Under the Disk Format column, select Thin Provision.
- Select a destination datastore that is different from the current datastore.
- Click Next and review the settings.
- Click Finish to start the Storage vMotion.