| 摘要 |
To provide a mirroring device which does not need a competition control function dedicated for a restoring process without halting other access commands during the restoring process of a mirroring. The mirroring device includes a pair of storage devices, a mirroring control unit which duplicates write data in the storage device in the case that a pair of storage devices are in a normal state and writes data in an available storage device in the case of a reduced state, a cache unit which stores input and output data and rewrites target data to be rewritten in the pair of storage devices, and a mirroring recovery unit which readouts date to the cache unit from the available storage device in the reduced state and recovers duplication of data by rewriting to the pair of storage devices when recovering from the reduced state to the normal state.
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