Storage apparatus and additional data writing method

1. A storage apparatus connected via a network to a host system issuing a content write request, the storage apparatus comprising:

a storage unit providing one or more containers composed of a specified storage area; and

a back up unit storing the content in the container in accordance with a backup request from the host system;

wherein the backup unit cuts out the content into one or more chunks, detects a duplicate chunk, which is a duplicate of a chunk stored in the container, from the cutout chunks, and additionally writes the chunk, other than the duplicate chunk, to the container where the duplicate chunk is stored;

wherein if the content includes a plurality of duplicate chunks and the plurality of duplicate chunks are stored in two or more containers, the backup unit stores the chunk other than the duplicate chunk in the container which stores a large number of duplicate chunks.

2. The storage apparatus according to claim 1 , wherein the storage area of the container is constituted from a basic area and an extended area;

the duplicate chunk is stored in the basic area; and

the chunk other than the duplicate chunk is stored in the extended area.

3. The storage apparatus according to claim 2 , wherein the storage unit stores a container index table corresponding to the basic area and the extended area of the container;

the container index table stores management information of the chunk stored in the container; and

the backup unit detects the duplicate chunk based on the management information of the chunk stored in the container index table.

4. The storage apparatus according to claim 3 , wherein when storing the chunk in the container, the backup unit stores the management information of the chunk in the container index table corresponding to the container.

5. The storage apparatus according to claim 3 , wherein the container index table stores chunk identification information for identifying the chunk, positional information of the chunk in the container, and management information including a chunk length of the chunk.

6. The storage apparatus according to claim 5 , wherein the chunk identification information for identifying the chunk is a message digest of the chunk.

7. The storage apparatus according to claim 1 , wherein if the content includes the plurality of duplicate chunks and the plurality of duplicate chunks are stored in the two or more containers, the backup unit detects reference timing of the duplicate chunk stored in the container with respect to each container and stores the chunk other than the duplicate chunk in the container regarding which the reference timing is early.

8. The storage apparatus according to claim 7 , wherein the backup unit manages reference timing of the container index table to which reference is made when detecting the duplicate chunk; and if the content includes the plurality of duplicate chunks and the plurality of duplicate chunks are stored in the two or more containers, the backup unit detects the reference timing of the container index table corresponding to the container with respect to each container index table and selects the container index table regarding which the reference timing is early.

9. The storage apparatus according to claim 3 , wherein the backup unit: manages a reference bit for referring to the container and the container index table and an update bit for updating the container and the container index table with respect to each chunk included in the content;

sets a flag of the reference bit if the chunk is the duplicate chunk; and

sets a flag of the update bit if the chunk is not the duplicate chunk.

10. An additional data writing method using a storage apparatus connected via a network to a host system issuing a content write request, the storage apparatus including a storage unit providing one or more containers composed of a specified storage area, and a back up unit storing the content in the container in accordance with a backup request from the host system,

the additional data writing method comprising:

a step executed by the backup unit cutting out the content into one or more chunks;

a step executed by the backup unit detecting a duplicate chunk, which is a duplicate of a chunk stored in the container, from the cutout chunks; and

a step executed by the backup unit additionally writing the chunk, other than the duplicate chunk, to the container where the duplicate chunk is stored; and

a step executed, if the content includes a plurality of duplicate chunks and the plurality of duplicate chunks are stored in two or more containers, by the backup unit storing the chunk other than the duplicate chunk in the container which stores a large number of duplicate chunks.

11. The additional data writing method according to claim 10 , wherein the storage area of the container is constituted from a basic area and an extended area;

the duplicate chunk is stored in the basic area; and

the chunk other than the duplicate chunk is stored in the extended area.

12. The additional data writing method according to claim 11 , wherein the storage unit stores a container index table corresponding to the basic area and the extended area of the container; and

the container index table stores management information of the chunk stored in the container; and

wherein the additional data writing method further comprises a fourth step executed by the backup unit, in the detecting a duplicate chunk step, detecting the duplicate chunk based on the management information of the chunk stored in the container index table.

13. The additional data writing method according to claim 12 , further comprising a step executed, when storing the chunk in the container, by the backup unit storing the management information of the chunk in the container index table corresponding to the container.

14. The additional data writing method according to claim 12 , wherein the container index table stores chunk identification information for identifying the chunk, positional information of the chunk in the container, and management information including a chunk length of the chunk.

15. The additional data writing method according to claim 14 , wherein the chunk identification information for identifying the chunk is a message digest of the chunk.

16. The additional data writing method according to claim 10 , further comprising a step executed, if the content includes the plurality of duplicate chunks and the plurality of duplicate chunks are stored in the two or more containers, by the backup unit detecting reference timing of the duplicate chunk stored in the container with respect to each container and storing the chunk other than the duplicate chunk in the container regarding which the reference timing is early.

17. The additional data writing method according to claim 16 , further comprising a step executed by the backup unit: managing reference timing of the container index table to which reference is made when detecting the duplicate chunk; and detecting the reference timing of the container index table corresponding to the container with respect to each container index table and selecting the container index table regarding which the reference timing is early if the content includes the plurality of duplicate chunks and the plurality of duplicate chunks are stored in the two or more containers.

18. The additional data writing method according to claim 12 , further comprising a step executed by the backup unit: managing a reference bit for referring to the container and the container index table and an update bit for updating the container and the container index table with respect to each chunk included in the content;

setting a flag of the reference bit if the chunk is the duplicate chunk; and

setting a flag of the update bit if the chunk is not the duplicate chunk.