'Update all the QoS in terms of a key and value.
svc_qos_keys saves all the supported QoS parameters. Going through
this dict, we set the new values to all the parameters. If QoS is
available in the QoS configuration, the value is taken from it;
if not, the value will be set to default.'

def update_vdisk_qos(self, vdisk, qos):

    for (key, value) in self.svc_qos_keys.items():
        param = value['param']
        if (key in qos.keys()):
            v = qos[key]
        else:
            v = value['default']
        self.ssh.chvdisk(vdisk, [('-' + param), str(v)])
