Abstract: A method and apparatus are disclosed for the temporary preservation of physical space occupied by modified or deleted data stored in parallel disk drive array data storage subsystems, and for the temporary preservation of associated virtual to logical mapping table entries that describe and locate such temporary physical space. The data storage subsystem functions as a conventional large form factor disk drive memory, using an array of redundancy groups, each containing N+M disk drives. The invention further relates to apparatus for the recording of the occurrence and the timing of changes to mapping table entries and to the processing of such recorded changes in a reverse time sequence to recover previously modified or deleted data, or in a forward time sequence to return data to a more current state.