A data management method includes determining the size of input data, storing the input data in a log block if the size of the input data is determined to be a write unit, and storing the input data in a partial block if the size of the input data is determined to be smaller than the write unit. The log block is a temporary block storing data of same addresses and the partial block is a temporary block storing data regardless of their addresses. The memory system includes a nonvolatile memory and a memory controller configured to control the nonvolatile memory. The memory controller is configured to temporarily store input data smaller than a write unit in a selected memory block even when the input data have different addresses.