virtual free

    def calculate_virtual_free_capacity(total_capacity,
                                        free_capacity,
                                        provisioned_capacity,
                                        thin_provisioning_support,
                                        max_over_subscription_ratio,
                                        reserved_percentage,
                                        thin):
        """Calculate the virtual free capacity based on thin provisioning support.
        :param total_capacity:  total_capacity_gb of a host_state or pool.
        :param free_capacity:   free_capacity_gb of a host_state or pool.
        :param provisioned_capacity:    provisioned_capacity_gb of a host_state
                                        or pool.
        :param thin_provisioning_support:   thin_provisioning_support of
                                            a host_state or a pool.
        :param max_over_subscription_ratio: max_over_subscription_ratio of
                                            a host_state or a pool
        :param reserved_percentage: reserved_percentage of a host_state or
                                    a pool.
        :param thin: whether volume to be provisioned is thin
        :returns: the calculated virtual free capacity.
        """

        total = float(total_capacity)
        reserved = float(reserved_percentage) / 100
        total_avail = total - math.floor(total * reserved)

        if thin and thin_provisioning_support:
            # OLD WAY
            #free = (total * max_over_subscription_ratio
            #        - provisioned_capacity
            #        - math.floor(total * reserved))
            
            # NEW way using defined terms in original cinder doc
            free = (total_avail * max_over_subscription_ratio
                    - provisioned_capacity)
        else:
            # Calculate how much free space is left after taking into
            # account the reserved space.
            free = free_capacity - math.floor(total * reserved)
        return free