This paper describes the design and implementation of backward chained clustered RDFS reasoning in 4store. The system presented, called "4s-reasoner", adds no overhead to the import phase and yet performs reasonably well at the query phase. We also demonstrate that our solution scales over clusters of commodity servers providing an optimal solution that balances infrastructure cost and performance over tested data sets with up to 500M triples. In addition we have shared our implementation under GNU license and a first release is available to be used by the community.