METHOD AND APPARATUS FOR GENERATING SNAPSHOT COPIES FOR DATA BACKUP IN A RAID SUBSYSTEM

Methods and apparatus for the rapid generation of a snapshot copy of the data stored in a RAID storage subsystem. In addition to the users configured RAID logical units, the present invention provides for the definition within the RAID controller of a logical RAID level one device having an operational half comprising the users defined logical unit(s) and having a non-operational mirror component. The user access data stored on the RAID subsystem by direct access to the users defined logical units. When a user directs a snapshot copy request to the operational, user defined logical units, the RAID controller responds by temporarily configuring available storage capacity (e.g. spare disk drives) in the RAID subsystem to perform the function of the non-operational mirror component of the logical RAID level one device. Restoring operation of the non-operational mirror component further causes the RAID controller to rebuild the content of the restored mirror component by copying the content of the user's configured device(s) to the temporary replacement mirror component. Following completion of the rebuild operation, the logical RAID level one device is restored to the status of having a non-operational mirror component. The data copied to the temporarily reconfigured available storage capacity is then returned to the user requesting the snapshot data for further processing as a backup.