1. A method of performing parity operations in a redundant data storage system that utilizes a plurality of data segments and at least two corresponding parity segments, wherein the parity segments are derived from the data segments and from parity coefficients corresponding to respective data segments, and wherein there are different parity operations involving different subsets of the parity coefficients, the method comprising the following steps: pre-selecting parity coefficient subsets for use in the different parity operations; storing all of the pre-selected parity coefficient subsets in a memory; when performing a particular parity operation, determining which of the stored subsets of parity coefficients is needed for the particular parity operation; reading the determined subset of parity coefficients from the memory; performing the particular parity operation with the subset of parity coefficients that was read from the memory: