A further point that's widely underappreciated: in modern systems, as demonstrated in the figure, random access to memory is typically slower than sequential access to disk. Note that random reads from disk are more than 150,000 times slower than sequential access; SSD improves on this ratio by less than one order of magnitude. In a very real sense, all of the modern forms of storage improve only in degree, not in their essential nature, upon that most venerable and sequential of storage media: the tape. (#)