Techniques for serving data to a plurality of clients in a client-server environment are provided. In one aspect of the invention, the technique provides a plurality of versions of data in which different versions have different overheads associated therewith. Individual clients are assigned to one of a plurality of quality-of-service classes. Requests are satisfied so that a client belonging to a high quality-of-service class is given preferential access to data versions which require higher overheads to serve.