If you do not set a volume for the quorum disk, you do not need to power off or on the external storage system because you do not use it.
Perform the procedure for Powering off external storage system, I/O at secondary site (GAD+UR), and then perform the procedure for Powering on external storage system, I/O at secondary site (GAD+UR), only when you set a volume for a quorum disk using an external storage system.