1. A method comprising: in a data storage device including a memory and an error correction coding (ECC) engine, performing: storing a first ECC page including a data block and first main ECC data to the memory, wherein the first main ECC data is usable by the ECC engine to correct errors in the first ECC page; and storing a second ECC page including first additional ECC data to the memory, wherein the first additional ECC data is usable by the ECC engine to correct errors in a single sub-block of multiple sub-blocks within the data block.