Abstract: A method of reading from a storage medium to recover a group of information sectors, each comprising a respective information payload. The medium stores redundancy data comprising a plurality of separate redundancy codes for the group, each code being a linear sum of terms, each term in the sum being the information payload from a different respective one of the information sectors in the group weighted by a respective coefficient of a set of coefficients for the redundancy code. The method comprises, after the redundancy data has already been stored on the medium: identifying a set of k? information sectors to be recovered; selecting k? of the redundancy codes; determining a square matrix E of the k? information sectors by the k? sets of coefficients of the selected codes; determining a matrix D being a matrix inverse of E; and recovering the k? information payloads from the inverse matrix D.