 In traditional HDDs, a rewritten file will generally occupy the same location on the disk surface as the original file, whereas in SSDs the new copy will often be written to different NAND cells for the purpose of wear leveling.The wear-leveling algorithms are complex and difficult to test exhaustively; as a result, one major cause of data loss in SSDs is firmware bugs.The following table shows a detailed overview of the advantages and disadvantages of both technologies.