| 摘要 |
PROBLEM TO BE SOLVED: To provide a magnetic disk device with improved reliability capable of performing a substituting processing without causing data loss in the case that an uncorrectable error is generated at the time of reading the logical sector of a magnetic disk medium. SOLUTION: The logical sector 33 is read and an error detection processing is performed. In the case that a correctable error is generated in the logical sector 33, data where the error is generated are corrected and the corrected data and a logical sector address are written onto a nonvolatile memory 50 simultaneously. In the case that the uncorrectable error is detected at the time of read access, the nonvolatile memory 50 is retrieved. In the case that a pertinent logical sector address is registered, registered data are transferred to a high-order host device 300, the substituting process of the uncorrectable error generated logical sector 33 is performed and the data registered in the nonvolatile memory 50 are written to a substituting area 32.
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