Method and apparatus for insuring recovery of file control information

Abstract

A method and apparatus for backing up the control information of a file system to a secondary storage system provides for a fast and reliable recovery of the file system in the event of an unscheduled hard stop of a computer processing system. The file system utilizes control information that is maintained in a cache memory of the computer processing system and a copy of the control information is periodically backed up to a first and second logical device in the secondary storage system. As part of each backup, a control stamp value unique to each iteration of the backup is written to a pair of unique control stamp locations on the logical devices, one control stamp location being written prior to the back up of the control information and the other control stamp location being written after the backup of the control information. In the event of an unscheduled hard stop of the computer processing system, the control information for the file system is quickly and accurately recovered by determining which of the two copies of the control information is accurate based on a comparison of the control stamp values in all four control stamp locations.