Storage apparatus and storage system

A system comprising:

• a storage apparatus used for storing data written into said storage apparatus;
• and
• a host apparatus for writing said data into said storage apparatus, wherein said storage apparatus comprises:
• a memory that allows an operation to be carried out in order to additionally write new write data into a storage area already used for storing previous write data so as to store said new write data in said storage area along with said previous write data;
• an input/output section configured to receive said new write data from said host apparatus in a write access made by said host apparatus, and
• a control section configured to write said new write data into said memory based on said write access made by said host apparatus and send a success notification to the host apparatus indicating completion of a previous write operation,
• wherein said previous write data is stored, based on said previous write operation, in a first physical page forming a pair in conjunction with a second physical page in said storage area,
• based on said write access made by said host apparatus, said control section performs an additional write operation to write said new write data into said storage area already storing said previous write data received from said host apparatus, and
• said new write data is stored in a physical page other than said first and second physical pages in said storage area, after said success notification is sent.