Tornado
Divided into a Front End and Back End component, Tornado combines and presents the content of multiple servers, offloading most of the work of servicing multiple reader connections
Tornado does this in a tightly integrated fashion not possible in caching schemes, allowing complete customization. Most importantly, a Tornado Front End installation requires very little disk (about 150GB) but can represent many Terabytes of spool controlled by a Tornado Back End. It can also serve an article from up to 4 separate, prioritized locations, if one server is offline or being moved, another will be transparently tapped.
Tornado relieves the load of the Tornado Back End so much that a given news service can more than triple its readership, with very little capital expenditure. In addition, Tornado allows further massive scalability, which will grow as your readership does, painlessly and for much less cost than any other solution