Shared Nothing architecture (SN) is a distributed computing architecture where each node is independent and self-sufficient, and there is no single point of contention across the system. Shared Nothing is popular for web development because of its scalability. As Google has demonstrated, a pure SN system can scale almost indefinitely simply by adding nodes in the form of inexpensive computers (*and an inexpensive OS like Linux), since there’s no single bottleneck to slow the system down. Two popular web development technologies, PHP and Ruby on Rails, both emphasize an SN approach, in contrast to technologies like J2EE that manage a lot of central state. An SN system may partition its data among many nodes (assigning different computers to deal with different users or queries), or may require every node to maintain its own copy of the application’s data, using some kind of coordination protocol.
* Google employs data centers full of low-cost commodity computers running a custom Red Hat Linux in several locations around the world to respond to search requests and to index the web. The server farms in the data centers are built using a shared nothing architecture. The indexing is performed by a program named Googlebot, which periodically requests new copies of web pages it already knows about. The more often a page updates, the more often Googlebot will visit. The links in these pages are examined to discover new pages to be added to its internal database of the web. This index database and web page cache is several terabytes in size. Google has developed its own file system called Google File System for storing all this data.