Storage system and control method therefor

A control method for a storage system,

• the storage system comprising a processor, a processor memory, a cache memory, and a storage apparatus, the storage system being coupled to a host computer in a manner that allows communication between the storage system and the host computer,
• the storage apparatus having a storage area comprising a first logical volume and a second logical volume,
• the control method comprising:
• a first step of storing, by the processor, in the cache memory, new data when a write request to write the new data in the first logical volume is received after reception of a first pair creating request, which is for storing, in the second logical volume, the same data that is stored in the first logical volume at present;
• and
• a second step of omitting copying, by the processor, to the second logical volume, data that is in the first logical volume at a time of reception of the first pair creating request when the data that is in the first logical volume at the time of reception of the first pair creating request is stored in the cache memory and is not copied to the second logical volume yet at a time of reception of a second pair creating request for storing present data of one of the first logical volume and the second logical volume in another of the first logical volume and the second logical volume.