Storage apparatus and method for controlling cache of storage apparatus

A storage apparatus that is connected to a host apparatus, the storage apparatus comprising:

• a memory that includes a save memory area and a cache memory area which temporarily stores data received from the host apparatus;
• a storage device that stores the data;
• and
• a processor, wherein the processor:
• controls a duplication process for specified data into an other storage apparatus at a point in time of a start of duplication,
• increments a checkpoint number when data blocks are reflected from the memory to the storage device,
• creates a first checkpoint list, wherein the checkpoint list includes a first list of data blocks and first checkpoint numbers that correspond to most recent data in the cache memory area,
• creates a second checkpoint list, wherein the checkpoint list includes a second list of data blocks and second checkpoint numbers that correspond to when data was reflected to the save memory area,
• saves, based on a comparison of the first checkpoint list and the second checkpoint list, a first data block into the save memory area when receiving an update request of the first data block in the cache memory area after the start of duplication,
• updates the first data block in the cache memory area to an updated data block,
• reads the first data block from the save memory area, and
• transmits the first data block to the other storage apparatus.