A data storage system may have a number of data storage devices that each have a non-volatile memory connected to a memory buffer. The memory buffer can consist of a map unit having a predetermined size. In receipt of a data sector into the map unit of the memory buffer, the data sector may be identified as a runt with a runt module connected to the memory buffer and the non-volatile memory. The runt module can generate and subsequently execute a runt handling plan to fill the size of the map unit before storing the filled map unit in the non-volatile memory.