Storage device and information management system

An information management system having a first storage device present at a first location, and a second storage device present at a second location, wherein at least the first storage device is provided with:

• a host interface connected to a host device and receiving data from the host device;
• memory connected to the host interface and saving data exchanged with the host device and control information relating to the data exchanged with the host device;
• a plurality of disk interfaces connected to the memory and performing control to read and write the data exchanged with the host device to and from the memory;
• a plurality of disk drives connected to the plurality of disk interfaces and storing data sent from the host device based on control of the plurality of disk interfaces;
• and
• a control processor for controlling reading and writing of data to and from a first logical volume generated using storage areas of the plurality of disk drives, performing control to write old data stored in the first logical volume into a second logical volume as per-generational differential data, and managing the differential data by providing in the area of the memory a snapshot management table for managing the relationships of the per-generational differential data stored in the second logical volume,
• wherein the snapshot management table is used to generate specific per-generational virtual logical volume, and
• the virtual logical volume is used to create a remote copy in the second storage device, and wherein a first bitmap showing an area where a differential occurred with respect to a previously created remote copy is created when updating the virtual logical volume, and
• a second bitmap showing the area of the differential data is created when writing the differential data to the second logical volume.