Those HGST MegaScale drives were cheap, designed for light loads, had only 800kh MTBF, 10^-14 UBER, and only a 3-year warranty. I suppose the low power from the 5400 or 5700 RPM produced a lot less heat than the typical "Hibachi" drives of the era, but even at 5-6W for 4TB that's a lot compared...