Fan speed on T430 at 2760 RPM constantly, irrespective of load

Worked it out - it is to do with the ThirdPartyPCIFanResponse setting within the iDRAC. I am using an "unsupported" PCIe GPU, so the ThirdPartyPCIFanResponse flag was set to Enabled, which results in a minimum of 2760 RPM on the system fan.

I checked it as follows:

$ sudo /opt/dell/srvadmin/bin/idracadm7 get System.ThermalSettings
[Key=System.Embedded.1#ThermalSettings.1]
#FanSpeedHighOffsetVal=55
#FanSpeedLowOffsetVal=20
#FanSpeedMaxOffsetVal=100
#FanSpeedMediumOffsetVal=35
FanSpeedOffset=Off
#MFSMaximumLimit=100
#MFSMinimumLimit=11
MinimumFanSpeed=255
ThermalProfile=Default Thermal Profile Settings
ThirdPartyPCIFanResponse=Enabled

I then disabled that setting as follows:

$ sudo /opt/dell/srvadmin/bin/idracadm7 set System.ThermalSettings.ThirdPartyPCIFanResponse Disabled

[Key=System.Embedded.1#ThermalSettings.1]
Object value modified successfully

And my fan speed instantly dropped to 1440 RPM

$ sudo ipmitool sdr elist | grep -i rpm
Fan1 | 30h | ok | 7.1 | 1440 RPM

I can hear myself think now!!!

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Note - you need Dell OpenManage installed to be able to run these commands; instructions here - http://linux.dell.com/repo/community/ubuntu/