Storage system and data processing method

A data processing method, which is executed in a storage system,

• the storage system including:
• a first storage device;
• a second storage device higher in I/O performance than the first storage device;
• a data amount reducing part configured to reduce a data amount of write data from a host computer;
• and
• a controller configured to provide the host computer with virtual volumes, each of which includes a plurality of logical areas,
• the data processing method including steps of:
• allocating, by the controller, a storage area of one of the first storage device and the second storage device to a logical area specified by the received write request after a write request to one of the virtual volumes is received from the host computer;
• storing, by the controller, data requested by the write request to be written in the allocated storage area;
• relocating the stored data between the first storage device and the second storage device;
• changing, by the controller, the storage area that is allocated to the specified logical area to a relocation destination storage area;
• managing, by the controller, an I/O load of the data and a reduction ratio of the data requested by the write request from the host computer to be written;
• calculating, by the controller, a load per capacity reduction unit of the data reduced by the data amount reduction unit by using an I/O count and an inverse number of the reduction ratio;
• determining, by the controller, whether or not data relocation is necessary by using the calculated load per capacity reduction unit;
• managing, by the controller, a first I/O load in a first determined period and a second I/O load of I/O from the host computer in a second determined period;
• determining, by the controller, whether to relocate data by using a load per capacity reduction unit that is based on the reduced data size and is calculated from the first I/O load and from the second I/O load;
• and
• relocating the data that is determined as needing relocation between the first storage device and the second storage device.