It was previously thought that there was a clear correlation between disk temperatures and failure rates; however, the studies undertaken by Google Inc. on the large disk population have revealed that the correlation is not as strong as it was assumed earlier. In the studies, S.M.A.R.T. data which were collected every few minutes during 9-month window of observation have been analyzed. Only average temperatures were taken into account. It was found that failures don't increase when the temperature increases. Moreover, the higher probability of failure rates was observed for the lower temperature ranges. The positive correlation has been detected only for the disks with temperatures greater than 500C.
However, 3 and 4 year old drives stand out. For such drives, the correlation between average temperatures and failure rates turned out to be more pronounced, probably due to then current HDD technology.
Thus, the studies show that the disk temperature affects the failure rate directly only for old drives and high temperature ranges (above 500C). For the moderate temperatures other factors affect failure rates much more strongly than temperatures do.