A memory system is disclosed, comprising a primary memory module, a secondary memory module, and a controller. The controller is configured to identify addresses in the primary memory module requiring correction, and is further configured to receive a memory access request identifying an address in the primary memory module. The controller is configured to determine whether the address is identified as requiring correction and, if it is not, to direct the memory access request to the primary memory module. If the address is identified as requiring correction, the controller is configured to direct the memory access request to the secondary memory module.