Large-scale storage system and data placement method in large-scale storage system

1. A large-scale storage system comprising:

a first storage module and a second storage module each connected to a computing machine, the first storage module and the second storage module being connected to each other by a network, wherein

the first storage module includes a first storage medium, and a first controller that configures a first volume from the first storage medium and that exercises control over a write process in such a manner that data is written to the first storage medium from the computing machine via the first volume and over a read process in such a manner that data stored in the first storage medium is read to the computing machine via the first volume,

the second storage module includes: a second storage medium, and a second controller that configures a second volume from the second storage medium and that exercises control over a write process in such a manner that data is written to the second storage medium from the computing machine via the second volume and over a read process in such a manner that data stored in the second storage medium is read to the computing machine via the second volume, and

the first controller:

determines whether second data, that is same as first data requested to be written to the first storage medium, is already stored in the second storage module when the first storage module receives a write request to the first volume from the computing machine,

determines whether to store the first data in the first storage medium or to refer to the second data in the second storage module in a case in which the second data is already stored in the second storage module, and

in determining whether to store the first data in the first storage medium or to refer to the second data in the second storage module in the case in which the second data is already stored in the second storage module, stores the first data in the first storage medium in a case in which a number of references to the second data exceeds a threshold.

2. The large-scale storage system according to claim 1 , wherein

the first controller compresses the first data and stores the compressed first data in the first storage medium.

3. The large-scale storage system according the claim 1 , wherein

the first controller determines whether to replicate data which is stored in the second storage module and which is being referred to, in the first storage medium of the first storage module in a case in which a read request from the computing machine to the first volume is to refer to the data which is stored in the second storage module.

4. The large-scale storage system according to claim 3 , wherein

the first controller cyclically determines whether to replicate the data which is being referred to.

5. The large-scale storage system according to claim 3 , wherein

in a case of determining to replicate the data which is being referred to as a result of determination as to whether to replicate the data which is being referred to, the first controller compresses the data to be replicated and records the compressed data in the first storage medium.

6. The large-scale storage system according to claim 3 , wherein

the first controller determines whether to replicate the data which is being referred to on a basis of process frequency information about data requested to be read or on a basis of the number of references to the data requested to be read.