Computer system, storage device and date updating method

A method implemented via a computer system including:

• a computer including a first processor manages a first virtual computer and a second virtual computer;
• and
• a storage system including a second processor provides a first virtual volume to the first virtual computer and a second virtual volume to the second virtual computer, an original data volume which stores an original data shared by the first virtual volume and the second virtual volume, and a differential data volume which stores a first differential data of the first virtual volume and a second differential data of the second virtual volume;
• the method implementing operations of:
• wherein if the first processor receives a first request to update a first data stored in a first virtual area of the first virtual volume, the first processor requests the storage system to store the first data in a first area of the original data volume, the first area corresponding to the first virtual area,
• wherein if the first processor receives a second request to update a second data stored in a second virtual area of the first virtual volume, the first processor requests the storage system to store the second data in a second area of the differential data volume, the second area corresponding to the second virtual area.