Internet companies including search engines (Google, Bing), social media companies (Facebook, Twitter), and email providers (Yahoo!, Outlook.com) are managing data stores measured in petabytes. On a daily basis these organizations handle all sorts of structured and unstructured data.
Assuming they put all their data in one repository, that could technically be thought of as a data lake. These organizations have adapted existing tools, and even created new technologies, to manage data of this magnitude in a field called big data.
The short version: big data is not a 100 GB SQL Server database or data warehouse. Big data is a relatively new field that came about because traditional data management tools are simply unable to deal with such large volumes of data. Even so, a single SQL Server database can allegedly be more than 500 petabytes in size, but Michael J. Swart warns us: if you’re using over 10% of what SQL Server restricts you to, you’re doing it wrong.
Incidentally, I’ll note that the term data swamp has a storied history here at Curated SQL.