DL380G6 Loud FAN Noise

Steps that explained below will reset NVRAM configuration for motherboard.
1) Power Off your Server and unplug power cords.
2) To prevent RAID configurations from losting, remove all of your disk.
3) You will see very little switch in front of battery.
4) Configure the number6 to on state
5) Power on server for 10 seconds, then power off and unplug the cords.
6) Configure the number 6 to off state again on switch.
7) Insert disks , power on server.

It works for me! Be carefull while changing switch states.