Disclosed is a method and apparatus for refreshing a copy of a data volume. In one embodiment of the method first and second data portions of a data volume are copied to first and second memory blocks, respectively, of a memory coupled to a computer system. First and second bits of a first map stored in memory are then set, wherein the first and second bits correspond to the first and second memory blocks, respectively. The first data portion of the data volume is modified after the first data portion is copied to the first memory block. A first bit in a second map stored in memory is set after data of the first data portion is modified. An instruction is generated to refresh the data contents of the first and second memory blocks. The first bit of the first map is cleared in response to generation of the refresh instruction.