Patent ID: 8677093

Claim:
A method of tier management of data, in a system which includes a host, a network, and a storage system coupled to the host via the network, the storage system having a memory, a plurality of virtual volumes, a plurality of logical volumes, and a plurality of physical media, the method comprising: performing a tier migration log information setup process which includes selecting an area specified by a virtual volume address and a logical volume address; determining a destination tier for the area based on a number of accesses to the area; and updating a tier migration log information by inputting the determined destination tier and a time; wherein for a specific area, the tier migration log information setup process provides destination tier and time information for the specific area during the updating; and performing a process using the tier migration log information to determine whether to migrate the specific area which includes loading a tier migration log from the tier migration log information by selecting a specific time prior to a current time; checking if a current tier of the specific area at the current time equals a destination tier for a time specified by the tier migration log which corresponds to the specific time, the tier migration log containing the destination tier and time information for the specific area; and if the current tier is not equal to the destination tier indicating that the specific area is not in the destination tier previously updated for the specific area according to the tier migration log for the time corresponding to the specific time, migrating the specific area to the destination tier specified by the tier migration log for the time corresponding to the specific time; and storing tier destination information which includes virtual volume name, virtual volume address, capacity, number of access, access per capacity, current tier, and destination tier, that are organized in a descending order of access per capacity; wherein the tier destination information is created based on virtual volume information of the logical volumes and media type from logical volume information of the logical volumes, the virtual volume information including virtual volume name, virtual volume address, logical volume name, logical volume address, number of access, and access capacity.