The paper introduces the Reservoir model and architecture for open federated cloud computing, addressing the limitations of current cloud computing offerings. The Reservoir project aims to create a modular, extensible cloud architecture that supports business service management and cloud federation, enabling an open, service-based online economy. The goal is to facilitate the dynamic partnership between cloud infrastructure providers, allowing them to form a seemingly infinite pool of IT resources while preserving their autonomy in technological and business decisions. The Reservoir approach leverages virtualization and autonomous management to achieve this, aiming to create a foundation for next-generation enterprise-grade cloud computing. The paper discusses the current state of cloud computing, highlighting issues such as limited scalability, lack of interoperability, and insufficient business service management support. It proposes a reference model and architecture that addresses these deficiencies, enabling on-demand delivery of IT services at competitive costs. The Reservoir model separates service providers and infrastructure providers, with service providers offering applications and leasing resources from infrastructure providers. The federation of collaborating sites forms a Reservoir cloud, where virtual execution environments (VEEs) are placed optimally to ensure high availability and performance. The paper also outlines the key components of the Reservoir architecture, including the service manager, virtual execution environment manager (VEEM), and virtual execution environment host (VEEH). These components work together to manage the deployment, provisioning, and monitoring of services, ensuring compliance with service-level agreements (SLAs). The architecture is designed to support different virtualization technologies and promote interoperability through standard, open, and generic protocols. Finally, the paper reviews related work in virtualization technologies, distributed management of virtualization, and business service management, emphasizing the importance of the proposed Reservoir model in overcoming existing challenges and enabling the full potential of cloud computing.The paper introduces the Reservoir model and architecture for open federated cloud computing, addressing the limitations of current cloud computing offerings. The Reservoir project aims to create a modular, extensible cloud architecture that supports business service management and cloud federation, enabling an open, service-based online economy. The goal is to facilitate the dynamic partnership between cloud infrastructure providers, allowing them to form a seemingly infinite pool of IT resources while preserving their autonomy in technological and business decisions. The Reservoir approach leverages virtualization and autonomous management to achieve this, aiming to create a foundation for next-generation enterprise-grade cloud computing. The paper discusses the current state of cloud computing, highlighting issues such as limited scalability, lack of interoperability, and insufficient business service management support. It proposes a reference model and architecture that addresses these deficiencies, enabling on-demand delivery of IT services at competitive costs. The Reservoir model separates service providers and infrastructure providers, with service providers offering applications and leasing resources from infrastructure providers. The federation of collaborating sites forms a Reservoir cloud, where virtual execution environments (VEEs) are placed optimally to ensure high availability and performance. The paper also outlines the key components of the Reservoir architecture, including the service manager, virtual execution environment manager (VEEM), and virtual execution environment host (VEEH). These components work together to manage the deployment, provisioning, and monitoring of services, ensuring compliance with service-level agreements (SLAs). The architecture is designed to support different virtualization technologies and promote interoperability through standard, open, and generic protocols. Finally, the paper reviews related work in virtualization technologies, distributed management of virtualization, and business service management, emphasizing the importance of the proposed Reservoir model in overcoming existing challenges and enabling the full potential of cloud computing.