Information processing apparatus, information processing method and storage system using cache to reduce dynamic switching of mapping between logical units and logical devices

An information processing method for an information storage system having a storage apparatus and a file sharing server,

• said storage apparatus comprising:
• storage devices for providing logical devices to store data, and
• a first processing unit providing virtual logical units based on a mapping relationship between the logical devices and the virtual logical units and being adapted to switch to the mapping relation dynamically according to an external request;
• and
• said file sharing server comprising:
• a cache memory including cache extents;
• and
• a second processing unit operative to provide the virtual logical units of the storage apparatus to a host system by using said cache extents, and manage mapping relationships between the logical devices and the virtual logical units;
• said method comprising:
• a first step of (1) requesting by said second processing unit a certain file from the storage apparatus;
• (2) reading data of the certain file from the corresponding logical device in said storage apparatus and storing said data in one of said cache extents of the cache memory;
• and (3) performing data I/O processing to data of said file stored in said cache extent according to a file access request given by said host system for accessing said file;
• and
• a second step of dynamically switching by said first processing unit the mapping relationship between the logical devices and the virtual logical units according to an external request.