def METHOD_NAME(self,fan_id):
    try:
        self.IPMI_FAN_REAR_SPEED[3] = 'Fan' + str(fan_id) + '_Rear_rpm'
        ret_status, ipmi_cmd_ret = getstatusoutput_noshell(self.IPMI_FAN_REAR_SPEED)
        if ret_status == 0:
            rdata = ipmi_cmd_ret.splitlines()[3].split(':')[1].split(' ')[1]
            return rdata
    except Exception:
        logging.error('Failed to execute : %s'%(' '.join(self.IPMI_FAN_REAR_SPEED)))