according to one aspect , a method for performance optimization of read functions in a memory system includes receiving , at the memory system , a read request including a logical address of a target data . the memory system includes a primary memory and a back - up memory that mirrors the primary memory . the method also includes searching a fault monitor table for an entry corresponding to the received logical address . the fault monitor table includes a plurality of entries that indicate physical locations of identified memory failure events in the primary memory and the back - up memory . based on locating an entry corresponding to the received logical address , the method further includes selecting one of the primary memory and the backup memory for retrieving the target data . the selection is based on contents of the fault monitor table .