Priority-based scheduling policies are commonly used to guarantee that requests submitted to the different service classes offered by cloud providers achieve the desired Quality of Service (QoS). However, the QoS delivered during resource contention periods may be unfair on certain requests. In particular, lower priority requests may have their resources preempted to accommodate resources associated with higher priority ones, even if the actual QoS delivered to the latter is above the desired level, while the former is underserved. Also, competing requests with the same priority may experience quite different QoS, since some of them may have their resources preempted, while others do not. In this paper we present a new scheduling policy that is driven by the QoS promised to individual requests. Benefits of using the QoS-driven policy are twofold: it maintains the QoS of each request as high as possible, considering their QoS targets and available resources; and it minimizes the variance of the QoS delivered to requests of the same class, promoting fairness. We used simulation experiments fed with traces from a production system to compare the QoS-driven policy with a state-of-the-practice priority-based one. In general, the QoS-driven policy delivers a better service than the priority-based one. Moreover, the equity of the QoS delivered to requests of the same class is much higher when the QoS-driven policy is used, particularly when not all requests get the promised QoS, which is the most important scenario. Finally, based on the current practice of large public cloud providers, our results show that penalties incurred by the priority-based scheduler in the scenarios studied can be, on average, as much as 193% higher than those incurred by the QoS-driven one.

In this work we introduce the EUBrazilCC federated cloud e-infrastructure based on Fogbow, a new middleware designed to support federation of IaaS cloud providers according to a novel approach. It is based on the provision of federation functionalities offered at a higher architectural level than current approaches by being deployed on top of the IaaS cloud orchestrators of each federation member. Fogbow is endowed with great flexibility due to the use of plugins that allow for the definition of precise interaction points between the federation middleware and the underlying cloud orchestrator. The resulting architecture, which relies on standards for conciliating different orchestrators' peculiarities, is thereby able to provide a common API to decouple federation functionalities from the orchestrator functionalities. Fogbow has been deployed to federate the private clouds of the members of the consortium of the EUBrazilCC project, and is also being used in an experimental federation that is part of the cloud initiative of the Brazilian National Research and Education Network (NREN) operator, as well as in an experimental deployment that aims at federating private clouds belonging to two large public companies in Brazil.

Cloud computing providers offer multiple service classes to deal with workload heterogeneity. Classes are distinguished by their expected Quality of Service (QoS), which is defined in terms of Service Level Objectives (SLO). A priority-based scheduling policy is commonly used to guarantee that requests submitted to the different service classes achieve the desired QoS. However, the QoS delivered during resource contention periods may be unfair to certain users. In this paper, we present a SLO-driven scheduling policy which takes the SLOs and actual QoS delivered for each request into account when making decisions. We used simulation experiments fed with traces from a production system to compare the SLO-driven policy with a priority-based one. In general, the SLO-driven policy delivered a better service than the priority-based one.

Many e-science initiatives are currently investigating the use of cloud computing to support all kinds of scientific activities. The objective of this chapter is to describe the architecture and the deployment of the EUBrazilCC federated e-infrastructure, a Research & Development project that aims at providing a user-centric test bench enabling European and Brazilian research communities to test the deployment and execution of scientific applications on a federated intercontinental e-infrastructure. This e-infrastructure exploits existing resources that consist of virtualized data centers, supercomputers, and even opportunistically exploited desktops spread over a transatlantic geographic area. These heterogeneous resources are federated with the aid of appropriate middleware that provide the necessary features to achieve the established challenging goals. In order to elicit the requirements and validate the resulting infrastructure, three complex scientific applications have been implemented, which are also presented here.