First responder parities for storage array

A computer program product for correcting erasures in a storage array, the computer program product comprising:

• a computer readable storage medium having program instructions embodied therewith, the program instructions readable by a processing circuit to cause the processing circuit to perform a method comprising:
• dividing data into a plurality of stripes for storage in a storage array comprising a plurality of storage locations, each stripe comprising M rows and N columns, each of the M rows including a number r of row parities, wherein r is greater than zero;
• dividing each stripe into two or more column sets, each column set comprising a respective set of two or more consecutive columns of the stripe;
• adding a respective first responder parity to each column set to enable an isolated erasure to be corrected by only accessing the two or more consecutive columns in the first responder parity's respective column set, wherein each first responder parity only provides parity information for the column set in which the first responder parity is located;
• and
• based on the isolated erasure in a column set, correcting the isolated erasure by reading data from only storage locations corresponding to the column set in which the isolated erasure occurred using the first responder parity of the column set.

A method for correcting erasures in a storage array, the method comprising:

• dividing data into a plurality of stripes for storage in a storage array comprising a plurality of storage locations, each stripe comprising M rows and N columns, each of the M rows including a number r of row parities, wherein r is greater than zero, and each of the N columns a number c of column parities, wherein c is greater than zero;
• dividing each stripe into two or more column sets, each column set comprising a respective set of two or more consecutive columns of the stripe;
• adding a respective first responder parity to each column set to enable an isolated erasure to be corrected by only accessing the two or more consecutive columns in the first responder parity's respective column set, wherein each first responder parity only provides parity information for the column set in which the first responder parity is located;
• adding at least one global parity to the stripe;
• based on the isolated erasure in a column set, correcting the isolated erasure by reading data from only storage locations corresponding to the column set in which the isolated erasure occurred using the first responder parity of the column set;
• and
• correcting a number of erasures that is greater than (r+1)(c+1)−1 using the row, column, and global parities.