what type of database google use?

Dears, have you any curious about "what type of database google use?" .

Google use primarily "A Distributed Storage System for Structured Data" Such as

Bigtable :- is a distributed storage system for managing
structured data that is designed to scale to a very large
size. . . for more download the document from here.

"http://labs.google.com/papers/bigtable.html"


Google also use Oracle and Mysql database for their some applications.

any more information from you is highly appreciated .