Patent ID: 8006111

Claim:
A method of operating a file server for power savings, the file server including active storage containing frequently accessed files, and active/inactive disk drives for containing infrequently accessed files, said method comprising: (a) successively migrating groups of the files from the active storage to respective evacuated ones of the active/inactive disk drives, the files in each group of files being migrated when the files in said each group of files become inactive in the active storage, wherein the files in said each group of files are selected to have a similar probability of access when access to the active/inactive disk drive containing said each group of files reaches an inactivity threshold for powering down the active/inactive disk drive containing said each group of files; and (b) powering down the disk drive containing said each group of files when access to the active/inactive disk drive containing said each groups of files reaches the inactivity threshold for powering down the active/inactive disk drive containing said each group of files; wherein said method further includes computing a respective expulsion time for each of the files in the active storage, the respective expulsion time specifying when said each of the files in the active storage should be migrated from the active storage to one of the active/inactive disk drives for power savings, and placing said each of the files in the active storage on an expulsion list ordered by the respective expulsion time, and at the respective expulsion times, successively migrating the files in each group of the files from the expulsion list to the active/inactive disk drive for containing said each group of files.