Some drives report a bogus reference temperature
Some drives have firmware that reports a reference temperature which is not just incorrect but unreasonably low. This causes FMA to fault drives even when their temperature is well within safe limits. In the affected drives from Segate and Western Digital this value is set to 40 degrees. This differs from the value used internally by PFA which is 60 degrees.
The solution I propose is that we tweak the logic in FMA so that the reference temperature is only used if it's above 40 degrees, otherwise we use a substitute value of 60 degrees, which is the true reference temperature of these particular drives. This is also likely to be the case for other drives reporting a reference temperature which is suspiciously low.