Patent ID: 8756199

Claim:
A computer system comprising: a client computer; a storage system for providing a first storage region and a second storage region; and a file service system coupled to the client computer and the storage system; wherein the performance of the first storage region is higher than that of the second storage region; wherein the file service system manages accessed file information including a plurality of partial accessed file lists, in which the files in each of the partial accessed file lists have been accessed by the client computer within the period of time specified for the corresponding partial accessed file list, and stores files, each including file meta-information and file data in the first storage region; wherein each of the file meta-information indicates a last accessed time by the client computer of the relevant file data; wherein the file service system selects at least one of the partial accessed file lists that satisfies migration policy information, and selects a candidate file from the files indicated in the selected at least one partial accessed file list based on the last accessed times indicated by the file meta-information; and wherein the file service system migrates the candidate file from the first storage region to the second storage region.