Patent ID: 8817412

Claim:
A magnetic disk device comprising: a first magnetic head corresponding to a first disk surface; a second magnetic head corresponding to a second disk surface; a skip processor which performs skip processing to prevent selection of the second magnetic head when writing is performed by the first magnetic head; at least one magnetic disk having the first disk surface or the second disk surface; a vibration sensor which detects vibrations around the magnetic disk; a temperature sensor which detects a temperature around the magnetic disk; an error rate measuring unit which measures an error rate of data read from the magnetic disk; a write environment detecting unit which detects a write environment being an index of whether the writing can be performed stably or not when the writing to the magnetic disk is performed, based on at least one of the vibration, the temperature and the error rate; a write data saving unit which selects the second magnetic head, and writes write data to the second disk surface through the second magnetic head by lowering a recording density as compared with the case of writing to the first disk surface through the first magnetic head, when the write environment is in a predetermined state; and a write data write-back unit which selects the first magnetic head, and writes the write data written on the second disk surface to the first disk surface through the first magnetic head, when the write environment is not in the predetermined state.