1. A computer implemented method of reservoir simulation in a data processing system, the data processing system comprising a unified pool of a plurality of processor clusters of processor nodes, at least one of the processor clusters being composed of processor nodes having different processing speeds that the processor nodes in another processor clusters, the computer implemented method comprising the steps of: (a) allocating available processor nodes from each of the processor clusters in response to a user request for a reservoir simulation; (b) performing a domain decomposition of reservoir data into blocks for the reservoir simulation; (c) assigning the allocated processor nodes to individual ones of the decomposed reservoir data blocks; and (d) performing the requested reservoir simulation in the allocated processor nodes.