Patent ID: 8127095

Claim:
A system, comprising: a processor; and a memory comprising program instructions, wherein the program instructions are executable by the processor to implement: file system software configured to assign and migrate data in a multi-class file system comprising a hierarchy of storage classes, wherein more actively accessed data are migrated to higher storage classes in the hierarchy of storage classes and less actively accessed data are migrated to lower storage classes in the hierarchy of storage classes, wherein migrated data remains online within the multi-class file system; a restore mechanism configured to restore the multi-class file system, wherein, in said restore, the restore mechanism is configured to: restore the higher storage classes; and restore the lower storage classes after completion of said restore of the higher storage classes; wherein the file system software is further configured to grant one or more applications access to the more actively accessed data on the higher storage classes after completion of said restore of the higher storage classes and prior to completion of said restore of the less actively accessed data on the lower storage classes.