Awesome.Possum,   It is by design that the fan will remain on, while power applied, in order to maintain cooling.    Hope this helps.        
Hi team! R720XD server (has lastest BIOS/iDRAC - 2.90 and 2.65.65) - 4th fan (from left to right side) still running after system shutdown, about 700 rpm.Is it possible to fix it or it's normal functioning?  BR,Slava
DELL R720XD fourth fan still running after system shutdown.