Another question on SO suddenly got me wondering what the largest database in the world is (and how big it could be). A quick Google search turned up this: the NSA call database, created by the U.S. National Security Agency. Supposedly this database contains over 1.9 trillion records containing details relating to phone calls placed through AT&T and Verizon from as far back as 2001.
Does anyone have any idea what kind of DB system was used for this database? 1.9 trillion records seems to me like a lot more than even your typical large-scale commercial databases would have. But maybe I'm wrong. I also didn't research this extensively by any means, so perhaps the claim that the NSA call database is the biggest in the world is flat-out false.
Still, I'm interested to know what kind of DBMS, if any, could reasonably deal with this many records.