Bag of Tasks Rescheduling within Real Grid Environments: Different Approaches

Providing Quality of Service (QoS) in Grid environments is still a challenging task because advance reservation of resources is not always possible. By contrast, scheduling the use of resources in advance is a way of enhancing the provision of QoS, without physically reserving them. However, in a Grid scenario fragmentation may appear as a logic result of the allocation process, leading to poor resource utilization. To try to avoid that problem a rescheduling technique has been developed and applied periodically depending on the existing fragmentation. Nevertheless, reallocating jobs in an optimal way is an NP-Hard problem. Consequently, simple and scalable ways of distributing and allocating those jobs into the resources are presented and evaluated in a real Grid environment involving heterogeneous computing resources distributed across different national organizations, highlighting the benefits of using them to increase the resource usage.