a recording element or a reproducing element in a head generates heat that decomposes lubricating agent adhered to a slider surface near the recording / reproducing element of the head . this decomposed lubricating agent leads to corrosion of the magnetic layer and the like of the magnetic disk . the lubricating agent undergoes volume expansion due to this corrosion , creating a protrusion on the magnetic disk surface to which the lubricating agent is adhered . the magnetic disk surface to which the lubricating agent is adhered comes into contact with the magnetic head , leading to friction with the protective layer , the magnetic layer , and the like . in the worst case , this can lead to secondary errors where data recorded on the magnetic layer is erased . to prevent such secondary errors , the present invention provides a hard disk drive including : a magnetic disk to which is applied a first lubricating agent formed as ; and a mechanism for supplying a second lubricating agent to the magnetic disk having an average molecular weight of no more than 2 , 400 and no less than 600 and formed as h och 2 cf 2 p q ocf 2 ch 2 oh .