Patent ID: 8826066

Claim:
A mirroring system connectable to a first storage unit and a second storage unit, comprising: a rebuild unit configured to rebuild data stored in a first storage unit to a second storage unit, wherein the rebuild unit, in a case where a rebuilding process by the rebuild unit has been interrupted, (1) resumes the interrupted rebuilding process if a first predetermined condition is satisfied and (2) resumes the interrupted rebuilding process if a second predetermined condition is satisfied even if the first predetermined condition is not satisfied, wherein the rebuild unit does not resume the interrupted rebuilding process while the first predetermined condition and the second predetermined condition are not satisfied, wherein the first predetermined condition is that the rebuild unit receives information which is sent from a host computer which is connectable to the mirroring system, and wherein the host computer sends the information to the mirroring system in a case where the host computer returns from power saving state, and does not send the information to the mirroring system in a case where the host computer returns from power off state.