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=35FanSpeedOffset=Off#MFSMaximumLimit=100#MFSMinimumLimit=11MinimumFanSpeed=255ThermalProfile=Default Thermal Profile SettingsThirdPartyPCIFanResponse=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 rpmFan1 | 30h | ok | 7.1 | 1440 RPM  I can hear myself think now!!!  -----  Note - you need Dell OpenManage installed to be able to run these commands; instructions here - [URL]   
Hi,  I am using a PE T430 at no load, and the fan is running at 2760 rpm, as per the SDR information (as per IPMI ipmitool). If I do some number crunching the cpu usage goes up significantly, but the fan speed stays the same.  Is there a way to make fan speed variable, such that it goes super low when idle, and only ramps up as needed? I have played around with Thermal in in the lifecycle controller but can't get that to make any difference.  I am running Ubuntu 17.10.  Thanks,  Viv 
Fan speed on T430 at 2760 RPM constantly, irrespective of load