Harnessing Shared Wide-area Clusters for Dynamic High End Services

Current trends in distributed computing have been moving towards the use of wide-area clusters that are managed by different entities. In this paper, we introduce middleware-level support to facilitate computational resource sharing with service guarantees using non-dedicated server systems in wide-area clusters. The aim is to ensure that sets of computational tasks submitted to such high end systems are completed reliably and in a timely fashion. Our approach develops methods that enhance basic job scheduling with information about the execution history and trust values for the computational nodes to which jobs are assigned. In essence, job scheduling is enriched with trust models constructed and maintained at runtime, and scheduling decisions are based on metrics that capture trust in remote server systems. An implementation of the approach is evaluated on Planetlab, with initial results demonstrating good success rates in completing jobs within their specific service level agreements, including under conditions of high system loads. Additional results are attained with a variant of the scheduling algorithm that uses redundancy to further improve the likelihood of meeting end user SLAs. A representative application considered in this paper is remote data visualization, where substantial computation must be applied to data before displaying it to end users. SLAs capture desired end-to-end delay, and distributed server or cluster systems are used to perform the required computations in a timely manner