Methods, computing systems and computer program products implement embodiments of the present invention that include arranging multiple storage devices as a RAID array and receiving, from a given storage device storing a dataset, a number of error messages exceeding a threshold. A mirrored subset of the dataset is retrieved from the given device, and a calculated subset of the dataset is retrieved from remaining devices in the RAID array. In a first embodiment, the mirrored subset is created first, and the calculated subset includes a relative complement of the mirrored subset with respect to the dataset. In a second embodiment, the calculated subset is created first, and the mirrored subset includes a relative complement of the calculated subset with respect to the dataset. The mirrored and the calculated datasets are stored to an additional storage device, and the given device is replaced with the additional device in the RAID array.