Is anyone actually sitting on zettabyte-scale data sets, as the introduction claims? There's a three year old xkcd "what-if" that guesstimates Google has about

Is anyone actually sitting on zettabyte-scale data sets, as the introduction claims? There's a three year old xkcd "what-if" that guesstimates Google has about 15 exabytes of data, and that presumably includes lots of different types of data (e.g., you're not going to run any analysis across youtube videos, gmails, and self-driving car telemetry).