Method for writing specific values last into data storage groups containing redundancy

摘要

The present invention comprises a method for enhancing data integrity during write operations in a data storage subsystem which comprises an array of redundant, interconnected disk drives. A data storage subsystem is disclosed which provides for writing data segments spread across N disk drives of the array and provides for generating and recording redundancy information spread across M disk drives. Redundancy information is used for reconstructing erroneous data in the case of a disk drive failure. It may be desirable to write a final portion of the data last, after other portions of the data and associated redundancy information have been recorded to the disk drives. The last portion of the data segments may contain information that validates the data. It is common to automatically generate the redundancy information as the data is written to the disk drives. The generated redundancy information is then later written to the disk drives. This presents a problem in that the last portion of the data is written to disks before correct redundancy information is written. The present invention discloses a method of writing data and associated redundancy information to eliminate this problem. A first portion of the data excluding the validation portion is written to disks as the redundancy information is accumulated. Next, the last portion is applied to the redundancy accumulator circuitry but is not yet written to the disks. The redundancy information of the data is now recorded to the disks. Finally, the last portion of the data is recorded to the disks. This method eliminates the period of time in which apparently valid data segments on disks are actually invalid because the associated redundancy information is not yet written to disk.