Storage array having multiple erasure correction and sub-stripe writing

A method of updating data in an array of storage devices having data stored in a plurality of stripes, each stripe including one corresponding block from each storage device, the method comprising:

• reading original data from a subset of data blocks in a target stripe, wherein said target stripe comprises a plurality of code words representing a systematic Reed-Solomon mapping of said data blocks and wherein said plurality of code words comprises said data blocks and a distinct plurality of redundancy blocks, and;
• reading original redundancy information from said plurality of redundancy blocks in the target stripe;
• determining a data difference between new data and the original data;
• determining a redundancy difference from the data difference;
• applying the redundancy difference to the original redundancy information to obtain updated redundancy information;
• writing the new data to said subset of data blocks in the target stripe;
• and
• writing the updated redundancy information to said plurality of redundancy blocks in the target stripe.

A data storage subsystem that comprises:

• an array of storage devices configured to store information in the form of a plurality of stripes;
• and
• a storage controller coupled to the storage devices and configured to write a plurality of data blocks and a plurality of redundancy blocks forming each stripe to said array, said storage controller comprising a combined encoder/decoder circuit,
• wherein during an encoding mode of operation, said combined encoder/decoder circuit is configured to generate said plurality of redundancy blocks using an nth order generator polynomial where n is 2 or greater,
• wherein during a decoding mode of operation, said combined encoder/decoder circuit is configured to calculate error terms from said plurality of data blocks and said plurality of redundancy blocks, and
• wherein said storage controller is configured to utilize said error terms to recover information from up to n failed storage devices in said array performing multiple erasure correction.