40 million rows of one column with 1 byte is probably fine in a reasonable desktop system. 40 Million rows of varying "blob" fields each containing a totally

40 million rows of one column with 1 byte is probably fine in a reasonable desktop system. 40 Million rows of varying "blob" fields each containing a totally different structure of data data, each with a gig or so of various entries... well, I would be surprised to see any current RDBMS manipulate this the way I want as an analyst with ease, efficiency, and speed. It's not the rows, per se, but the size, variability, and in some cases, the velocity of the data that start to tax RDBMS. Anything with a consistent and relatively simple structure, even with long-and-many rows, can be handled in many modern RDBMS. But once you start varying the data per row, and mixing different levels of atomicity, the Big Data systems tend to provide more flexibility and ease, imho.