Allocating substitute area capacity in a storage system using flash memory packages

A system comprising:

• a first storage system including a first controller and a plurality of flash packages connected the first controller;
• and
• a second storage system coupled to the first storage system, which includes a second controller and a plurality of hard disk drives connected the second controller, the hard disk drives providing a logical device to a host computer,
• wherein the first controller is configured to create a logical device provided to the host computer as a copy destination for copying data in the logical device provided by the hard disk drives, and allocate to the created logical device, at least a first storage area with a first capacity and second storage area with a second capacity from storage area provide by the flash packages, the first capacity being a capacity which the host recognizes, the second storage area being provided as a substitute area,
• wherein the second capacity is calculated based on write access frequency for the logical device provided by the hard disk drives, and
• wherein the second capacity is calculated based on both the write access frequency for the logical device provided by the hard disk drives and a useful life span set for the created logical device.