Clusters of Computers have become a costeffective alternative for parallel and distributed computing systems processing computationally intensive tasks. Normally, clusters are composed of high performance computational nodes linked together by low-latency, high-bandwidth interconnection networks. With the advent of modern optical networking technologies, latency in long-distance links is close to that of local-area links. By using Service Address Routed (SAR) optical networks, NEOS-based clusters can be used transparently as single, tightly-coupled clusters of computers, regardless of the distance between their components while keeping a simple service-oriented interface. A performance-wise analysis of such clusters is presented in this work.