The adoption of cloud computing is still limited by several legal concerns that customers may have, such as data sovereignty. In cloud computing, data can be physically hosted in sensible locations , resulting in a lack of control for companies. In this context, we present the Nu@ge project, which aims at building a federation of container-sized datacenters in the French territory. Nu@ge provides a software stack that enables companies to interconnect independent datacenters in a national mesh. A software architecture is presented and implemented as a federation of small datacenters deployed in France. The proposed architecture enables cooperation between local customized-cloud managers and a federation-wide middleware. It uses monitoring information from facilities and performance indicators from physical servers for managing the system, preventing incidents and considering energy efficiency. Additionally, a prototype of a container-sized datacenter has been validated and patented. KEYWORDS cloud federation, energy-aware scheduling, IaaS 1 INTRODUCTION Cloud computing represents a significant evolution of information and communications technology in usage and organization. It allows companies to increase their competitiveness by lowering IT infrastructure costs and improving quality of service. This field is an opportuinity to new markets and business models as it is expected to grow up to 29% per year until 2019. 1 Despite its benefits to users, cloud computing raises several concerns of applications, data storage, and processing. Cloud providers reveal few information about geographical location and the way to process of data and applications. As information converted and stored in binary digital form is subject to the laws of the country in which it is located, several concerns are raised from a legal standpoint. Third-party entities or governments could take control of sensible data, and legal protections may not apply if one's data are located outside her country. Additionally, data from a company could be physically hosted with data from others. This causes security risks as one company may attempt to access data of another. The Nu@ge consortium* comprises 6 SMEs (small and medium-sized enterprise) and 2 research teams aiming to create cloud technology that is open to heterogeneous hardware and software stacks, spread on *Nu@ge is a research project funded by the FSN (Fund for the Digital Society, BPI France) as part of the Investissement d' Avenir program. http://www.nuage-france.fr a regional network among France and that uses low-energy consumption and ecological datacenters. This Nu@ge project is a large effort that tackles several challenges. In this work, we describe a federated architecture to provision virtual clusters of resources over the network while providing administrators with a control over data location and quality of service. Our solution is based on innovative container-sized datacenters that enables deployment of a cost-effective and high-performance datacenter environment in any location, meshing regional company-owned datacenters. This paper is structured as follows. Section 2 introduces the related work. Section 3 presents the Nu@ge architecture and the associated technical choices. The architecture is presented in Section 4 while the prototype is described in Section 5. Section 6 discusses an evaluation of energy efficiency, and Section 7 presents the energy-aware adaptive placement of tasks on server. Section 8 concludes the paper. 2 BACKGROUND AND RELATED WORK This section presents related work in the context of cloud providers and existing cloud federation approaches. Then, we detail the notion of modular datacenters and its expected features. Finally, we justify the choice of implementing our own distributed storage solution and the different energy-aware scheduling mechanisms.