A memory system for a data processing apparatus includes a fault management unit, a memory controller (such as a memory management unit or memory node controller), and one or more storage devices accessible via the memory controller and configured for storing critical data. The fault management unit detects and corrects a fault in the stored critical data, a storage device or the memory controller. A data fault may be corrected using a copy of the data, or an error correction code, for example. A level of failure protection for the critical data, such as a number of copies, an error correction code or a storage location in the one or more storage devices, is determined dependent upon a failure characteristic of the device. A failure characteristic, such as an error rate, may be monitored and updated dynamically.