摘要 |
The present invention uses the storage resources of a storage system effectively, thereby reducing the cost of the storage system and improving its usability. The storage system comprises a first storage apparatus and a second storage apparatus. When a host writes data to a virtual volume, the data are written into a pool area. A management table associates an address in the virtual volume with a pointer indicating the data stored in the pool area. The usage amount of the pool area is monitored. When the usage amount of the pool area reaches a predetermined value, a search for available capacity is performed. An unused external volume is detected and associated with an externally connected volume. The data stored in the pool area are then copied to the externally connected volume.
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