5130-pwr ,风扇太响，用了fan prefer-direction 之后还是太响

<H3C>dis fan Slot 1: Fan 1:  State    : FanDirectionFault Airflow Direction: Port-to-power Prefer Airflow Direction: Power-to-port Fan 2:  State    : Normal Airflow Direction: Power-to-port Prefer Airflow Direction: Power-to-port

<H3C>%Jan  1 00:29:01:162 2013 H3C STP/6/STP_NOTIFIED_TC: Instance 0's port Ten-GigabitEthernet1/0/25 was notified a topology change.
<H3C><H3C>%Jan  1 00:29:03:830 2013 H3C STP/6/STP_NOTIFIED_TC: Instance 0's port Ten-GigabitEthernet1/0/25 was notified a topology change.
<H3C><H3C>sysSystem View: return to User View with Ctrl+Z.[H3C]fan prefer-direction slot 1 port-to-power[H3C]%Jan  1 00:29:12:052 2013 H3C DEV/1/FAN_DIRECTION_NOT_PREFERRED: Fan 2 airflow direction is not preferred on slot 1, please check it.%Jan  1 00:29:12:852 2013 H3C DEV/5/FAN_RECOVERED: Fan 1 recovered.%Jan  1 00:29:13:090 2013 H3C STP/6/STP_NOTIFIED_TC: Instance 0's port Ten-GigabitEthernet1/0/25 was notified a topology change.%Jan  1 00:29:15:779 2013 H3C STP/6/STP_NOTIFIED_TC: Instance 0's port Ten-GigabitEthernet1/0/25 was notified a topology change.%Jan  1 00:29:24:102 2013 H3C STP/6/STP_NOTIFIED_TC: Instance 0's port Ten-GigabitEthernet1/0/25 was notified a topology change.%Jan  1 00:29:26:779 2013 H3C STP/6/STP_NOTIFIED_TC: Instance 0's port Ten-GigabitEthernet1/0/25 was notified a topology change.
[H3C][H3C][H3C][H3C]dis fan4%Jan  1 00:29:37:781 2013 H3C STP/6/STP_NOTIFIED_TC: Instance 0's port Ten-GigabitEthernet1/0/25 was notified a topology change.%Jan  1 00:29:39:779 2013 H3C STP/6/STP_NOTIFIED_TC: Instance 0's port Ten-GigabitEthernet1/0/25 was notified a topology change.
 Slot 1: Fan 1:  State    : Normal Airflow Direction: Port-to-power Prefer Airflow Direction: Port-to-power Fan 2:  State    : FanDirectionFault Airflow Direction: Power-to-port Prefer Airflow Direction: Port-to-power