In addition to what others said, when you want to analyze multiple datasets the biggest problem is to store all that on a single machine or even a machine with

In addition to what others said, when you want to analyze multiple datasets the biggest problem is to store all that on a single machine or even a machine with network-attached storage. Eventually you will start hitting the bounds of I/O which is what big data tries to solve by moving processing units closer to the data storage (in theory). In short, not all problems are big data problems.