Providing quality of service to prioritized clients with dynamic capacity reservation within a server cluster

A computer-implemented method for delivering a level of quality of service for a client requesting data in a connection arrangement including a server and a plurality of clients assigned one of a plurality of classes, wherein the determination of the level of quality of service includes estimating an arrival rate of potential future requests of at least one class of the plurality of classes, determining a capacity of the at least one data server, determining a current load of the server, reserving a capacity for at least the one class of the plurality of classes according to an estimated arrival rate, assigning the server to the client, and serving the data to the client from an assigned data server, wherein an amount of capacity is allotted to the client according to the level of the quality of service.