Many of the ideas that drive modern cloud computing, such as server virtualization, network slicing, and robust distributed storage, arose from the research community. But because today's clouds have particular, non-malleable implementations of these ideas "baked in," they are unsuitable as facilities in which to conduct research on future cloud architectures. This project creates CloudLab, a facility that will enable fundamental advances in cloud architecture. CloudLab will not be a cloud; CloudLab will be large-scale, distributed scientific infrastructure on top of which many different clouds can be built. It will support thousands of researchers and run hundreds of different, experimental clouds simultaneously. The Phase I CloudLab deployment will provide data centers at Clemson (with Dell equipment), Utah (HP), and Wisconsin (Cisco), with each industrial partner collaborating to explore next-generation ideas for cloud architectures CloudLab will be a place where researchers can try out ideas using any cloud software stack they can imagine. It will accomplish this by running at a layer below cloud infrastructure: it will provide isolated, bare-metal access to a set of resources that researchers can use to bring up their own clouds. These clouds may run instances of today's popular stacks, modest modifications to them, or something entirely new. CloudLab will not be tied to any particular particular cloud stack, and will support experimentation on multiple in parallel. The impact of cloud computing outside the field of computer science has been substantial: it has enabled a new generation of applications and services with direct impacts on society at large. CloudLab is positioned to have an immediate and substantial impact on the research community by providing access to the resources it needs to shape the future of clouds. Cloud architecture research, enabled by CloudLab, will empower a new generation of applications and services which will bring direct benefit to the public in areas of national priority such as medicine, smart grids, and natural disaster early warning and response.