Patent ID: 8533157

Claim:
A management computer for creating and managing snapshots of one or more generations, connected to a first storage system providing an operational volume storing data used by a host computer and a second storage system and third storage system each providing difference volumes storing difference data between the operational volume at a time of creation of a relevant snapshot, the management computer comprising: a control unit for controlling storing of the difference data in the second or the third storage system, in response to data writing from the host computer, a memory including a snapshot arrangement table for managing a relation between the snapshots and the difference volumes, and a monitoring unit for showing a certain trigger of difference volumes relating to a power supply for the second or the third storage system, wherein the second storage system stores is configured to store a management table for managing a plurality of snapshots corresponding to the difference volume of the second storage system, and the third storage system is configured to store a management table for further storing specified inheritance information to inherit content of the management table of the second storage system, wherein, in the snapshot arrangement table, a first snapshot is related to a first differential volume in the second storage system, a second snapshot is related to a second differential volume in the third storage system, data of the first snapshot is provided by data in the first differential volume and data in the second differential volume and data in the operational volume, and data of the second snapshot is provided by data in the second differential volume and data in the operational volume, wherein, when the control unit detects that the first snapshot related to the first differential volume does not receive a predetermined access during a pre-determined period the control unit is configured to confirm the status of the difference volume, and to determine to stop the power supply of the second storage system.