Storage system and data replication method in storage system

A storage system including a plurality of controllers and capable of creating a snapshot, which is a replication of a logical volume, wherein:

• the logical volume or the snapshot to be handled by the controller is assigned to the controller;
• a log structured area which stores data of the logical volume or the snapshot, and a meta information area which stores meta information of the data appended to the log structured area, are assigned to the controller;
• the controller comprises a data control unit which appends the data of the logical volume to the log structured area, and a data management unit which stores the meta information of the data appended to the log structured area by the data control unit in the meta information area;
• the meta information is composed of meta information of a first tier and meta information of a second tier which correlate location information of the data in the logical volume and location information of the data in the log structured area, wherewith the meta information of the first tier is information which correlates the location information of the data in the logical volume and a storage location of the meta information of the second tier related to that data, and the meta information of the second tier is information which manages the location information of the data in the log structured area;
• when creating a snapshot of the logical volume, the data management unit creates, in the same meta information area as a replication source, a replication of the meta information of the first tier stored in a plurality of meta information areas assigned to a plurality of controllers;
• and
• the data control unit of the controller pertaining to the meta information area in which the replication of the meta information of the first tier was created accesses the data of the log structured area from the logical volume based on the meta information of the second tier referenced based on the meta information of the first tier, and accesses the data of the log structured area from the snapshot based on the meta information of the second tier referenced based on the replication of the meta information of the first tier.