Abstract: Embodiments of the invention improve the security of data written on a magnetic disk by performing re-allocation processing starting from a sector whose defect is large in automatic re-allocation processing. According to one embodiment of the present invention, after the reliability of each of data sectors that have been read out from a magnetic disk according to a read command is determined, re-allocation processing on the data sectors is performed in the order of increasing reliability. As a result, within a limited period of time, it is possible to replace by priority a data sector where there is a high possibility that data recovery will be unable to be achieved. This makes it possible to increase the security of data and the reliability of the HDD. The reliability of each data sector is determined on the basis of the number of bytes corrected by ECC.

Abstract: Embodiments in accordance with the present invention provide an auxiliary storage device that prevents performance degradation and collects data useful for buffer failure analysis. In one embodiment, a data set including user data and cyclic redundancy check (CRC) information is temporarily stored in a buffer. If a CRC error is detected in a data set that is read from the buffer during a data write or data read, the contents of the data set and the affected buffer address are recorded on a nonvolatile recording medium. Further, the buffer address is disabled. This makes it possible to store the data for reproducing a soft error that occurs in the buffer and prevent the performance of the auxiliary storage device from being degraded by a buffer error.

Abstract: Embodiments of the invention improve the security of data written on a magnetic disk by performing re-allocation processing starting from a sector whose defect is large in automatic re-allocation processing. According to one embodiment of the present invention, after the reliability of each of data sectors that have been read out from a magnetic disk according to a read command is determined, re-allocation processing on the data sectors is performed in the order of increasing reliability. As a result, within a limited period of time, it is possible to replace by priority a data sector where there is a high possibility that data recovery will be unable to be achieved. This makes it possible to increase the security of data and the reliability of the HDD. The reliability of each data sector is determined on the basis of the number of bytes corrected by ECC.