A policy determining unit (48a) determines an allocation method for blocks on the basis of information on a hierarchical policy stored in a policy management table (42) and information on a volume stored in a volume management table (46). Then, on the basis of the determination result performed by the policy determining unit (48a), a first allocating unit (48b) performs allocation on the basis of the specified capacity and a second allocating unit (48c) performs allocation on the basis of the specified percentage for each volume.
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