Storage system and method for efficiently utilizing storage capacity within a storage system

A method for operating a storage system that includes a first storage apparatus and a second storage apparatus,

• the first storage apparatus including a first storage controller that manages a first pool that is a storage area provided by a plurality of physical disks and managed as a set of unit storage areas forming the storage area, and at least one logical volume created from the unit storage areas in the first pool,
• the first storage controller including a first configuration information holding unit having first configuration information holding an association among a pool identifier that is an identifier for identifying the first pool, a volume identifier that is an identifier for identifying the logical volume created from the first pool, and a unit storage area identifier that is an identifier for identifying the unit storage areas forming the logical volume,
• the second storage apparatus communicably connected to the first storage apparatus, and including a second storage controller that manages a second pool having a same configuration as that of the first pool and at least one logical volume created from the unit storage areas in the second pool,
• the second storage controller including a second configuration information holding unit having second configuration information holding an association among a pool identifier that is an identifier for identifying the second pool, a volume identifier that is an identifier for identifying the logical volume created from the second pool, and a unit storage area identifier that is an identifier for identifying the unit storage areas forming the logical volume,
• each of the first storage apparatus and the second storage apparatus including:
• an LU map processing part that manages LU mapping specifying association between an identifier of a logical volume recognized by an external apparatus connected to the first and second storage apparatuses and a volume identifier being an identifier of the logical volume used in the storage apparatus,
• a VVol processing part that creates a virtual volume provided to the external apparatus and controls a capacity of the virtual volume by assigning a segment that is the unit storage area to the created virtual volume, and
• a segment processing part that manages an association relationship among a volume identifier of the logical volume forming the pool, the segment assigned to the virtual volume, and the logical volume,
• the method being performed by a pool merge processing part provided in the second storage apparatus, the method comprising:
• specifying the logical volume included in the first pool by acquiring the first configuration information from the first configuration information holding unit;
• associating an external volume identifier with the specified logical volume in the first storage apparatus, the external volume identifier being used by the second storage controller to identify and manage the logical volume as an external volume that is a virtual volume in the second storage apparatus;
• and
• rewriting the acquired first configuration information so that the pool identifier for identifying the first pool is rewritten to the pool identifier for identifying the second pool, the unit storage area identifier for identifying the unit storage areas in the first pool is rewritten to an identifier that is different than the unit storage area identifier for identifying the unit storage areas in the second pool and the volume identifier of the logical volume included in the first pool is rewritten into the external volume identifier, and
• adding contents of the rewritten first configuration information to the second configuration information in order to enable the second storage apparatus to utilize the logical volume created from the first pool.