Patent ID: 8583882

Claim:
A storage subsystem comprising: a storage apparatus having a plurality of types of storage devices whose processing performance is different from each other; and a controller configured to manage, as an access object for an access requester, a tier storage file system configured by integrating a plurality of file systems including a file group configured in a storage area of the storage apparatus and virtually hierarchize the integrated plurality of file systems into a plurality of storage tiers; and change a storage tier to which each file system belongs, based on a plurality of pieces of policy information that set a migration condition for each file system, wherein the controller: manages the relationship between each file system and a tier level of a storage tier, to which each file system belongs, using a tier number change management table by associating the storage tier with a registered generation based on the time of registration; and manages the plurality of pieces of policy information, the plurality of pieces of policy information including at least the relationship between a tier level of a migration destination storage tier of each file system and the registered generation, using a migration policy management table, and wherein if a storage tier constituted from a new file system is to be added as a new storage tier to the plurality of storage tiers, the controller: adds a new registered generation to the tier number change management table and adds an entry corresponding to the new registered generation to the tier number change management table, the entry including the plurality of storage tiers and each file system corresponding to the registered generation preceding the new registered generation; changes a tier level of a storage tier affected by the addition of the new storage tier and updates the tier number change management table by adding the new storage tier as an entry corresponding to the storage tier the new registered generation in the tier number change management table; adds new policy information, in which a condition for migrating the new file system is set, to the migration policy management table and updates a registered generation of a storage tier which is a migration destination of the new file system, the storage tier which is the migration destination of the new file system being the new storage tier, from among registered generations in the migration policy management table, to the new registered generation; and updates the migration policy management table by adding the new registered generation as a registered generation of the new policy information.