Clouds must be efficient to provide useful fault-tolerance and scalability, but they also must be easy to use. CloudI (pronounced "cloud-e" /klaʊdi/) is an open source cloud computing platform that is most closely related to the Platform as a Service (PaaS) clouds. CloudI differs in a few key ways, most importantly: software developers are not forced to use specific frameworks, slow hardware virtualization, or a particular operating system. By allowing cloud deployment to occur without virtualization, CloudI leaves development process and runtime performance unimpeded, while quality of service can be controlled with clear accountability.