Powervault 114T

I can't find a description for the function of the led light on the front of this unit.  To the left of the power light is a light with what looks like to me a fan symbol.  It has an led light next to it and it is solid yellow.  The unit is working fine and I checked the vents in the rear and they both appear to be blowing out air.

Can anyone explain or point me to a source for how this led functions?