'Get the current value for the thin provisioning ratio.
If pure_automatic_max_oversubscription_ratio is True we will calculate
a value, if not we will respect the configuration option for the
max_over_subscription_ratio.'

def _get_thin_provisioning(self, provisioned_space, used_space):

    if (self.configuration.pure_automatic_max_oversubscription_ratio and (used_space != 0) and (provisioned_space != 0)):
        thin_provisioning = (provisioned_space / used_space)
    else:
        thin_provisioning = self.configuration.max_over_subscription_ratio
    return thin_provisioning
