This chapter gave a whirlwind tour of where Hadoop came from, its evolution, and why the version 2 release is such a major milestone. We also described the emerging market in Hadoop distributions and how we will use a combination of local and cloud distributions in the book.

Finally, we described how to set up the needed software, accounts, and environments required in subsequent chapters and demonstrated how to pull data from the Twitter stream that we will use for examples.

With this background out of the way, we will now move on to a detailed examination of the storage layer within Hadoop.