"..the holy grail has always been a helium-filled drive. Helium offers several advantages arising from its very low density and very high thermal conductivity. It takes much less power to run the spindles; cooling of the VCM and preamp is greatly improved; and temperature differentials within the drive almost disappear. The most important gain is from the reduction of internal turblulence and buffeting of the actuator and disks."
-- from "Future hard disk drive systems," Roger Wood, Journal of Magnetism and Magnetic Materials 321 (2009) 555-561