In systems consisting of multiple clusters of processors which are interconnected by relatively slow communication links and which employ space sharing for scheduling jobs, such as our Distributed ASCI 1 Supercomputer (DAS), coallocation, i.e., the simultaneous allocation of processors to single jobs in different clusters, may be required. We study the performance of co-allocation by means of simulations for the mean response time of jobs depending on the structure and sizes of jobs, the

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... ing policy, and the communication speed ratio. Our main conclusion is that for current communication speed ratios in multiclusters, coallocation is a viable option.