FIG. 2 is a diagram for description of an example of processing for writing data into SSDs;

FIG. 3 is a diagram for description of an example of processing at the time when an SSD is newly provided;

FIG. 4 is a diagram for description of second-order distribution;

FIG. 5 is a diagram illustrating an example of a virtual volume management table;

FIG. 6 is a diagram illustrating an example of an extent configuration management table;

FIG. 7 is a diagram illustrating an example of an extent state management table;

FIG. 8 is a diagram illustrating an example of a PG management table;

FIG. 9 is a diagram illustrating an example of an SSD block management table;

FIG. 10 is a diagram illustrating an example of a life statistics table;

FIG. 11 is a flow chart for description of an example of actions of a computer system;

FIG. 12 is a flow chart for description of an example of write processing;

FIG. 13 is a flow chart for description of an example of open processing;

FIG. 14 is a flow chart for description of an example of garbage collection processing;