[victoria][cinder] Default Storage type

Hi, I am creating nova instance with cinder backed iscsi storage. I have created multiple storage types. But my launched instance from image use storage type __DEFAULT__ for flavor's root volume. I have changed default_volume_type to mystoragetype in cinder.conf but instances root volume still goes in __DEFAULT__ storage type. However new volume creation in mystoragetype is successful. Need help, how can I set instance root volume storage type during its deployment ? Regards, Malik Obaid