Abstract: An apparatus is provided having a memory device and associated access control circuitry, and an additional memory device and associated additional access control circuitry. Redundant data generation circuitry generates, for a given block of data having an associated given memory address, an associated block of redundant data for use in an error detection process. The access control circuitry is arranged to store, at a location in the memory device determined from the given memory address, at least a portion of the given block of data and a first copy of the associated block of redundant data, and the additional access control circuitry is arranged to store, at a location in the additional memory device determined from the given memory address, any remaining portion of the given block of data not stored in the memory device and a second copy of the associated block of redundant data.