'Return spec for file-backed virtual disk creation.'

def _get_virtual_disk_create_spec(self, size_in_kb, adapter_type, disk_type):

    cf = self._session.vim.client.factory
    spec = cf.create('ns0:FileBackedVirtualDiskSpec')
    spec.capacityKb = size_in_kb
    spec.adapterType = VirtualDiskAdapterType.get_adapter_type(adapter_type)
    spec.diskType = VirtualDiskType.get_virtual_disk_type(disk_type)
    return spec
