A non-volatile data storage device includes memory cells arranged in a plurality of blocks and a memory controller coupled to the memory cells for controlling operations of the memory cells. The memory controller is configured to determine if a given block is a bad m-bit multi-level block. In an m-bit multi-level block, each memory cell is an m-bit multi-level cell (MLC), m being an integer equal to or greater than 2. Upon determining that the given block is a good m-bit multi-level block, the memory controller assigns the given block to be an m-bit multi-level user block. Upon determining that the given block is a bad m-bit multi-level block, the memory controller determines if the given block is a good n-bit block. In an n-bit block, each memory cell is an n-bit cell, n being an integer less than m. Upon determining that the given block is a good n-bit block, the memory controller assigns the given block to be an n-bit user block or an n-bit write-buffer block.