Abstract: The emergence of open source software for cloud computing facilitates the building of cloud computing plat- forms, but meanwhile it challenges the choosing of appropriate ones from these pool of software. I}o figure out how to build a cloud computing platform,research on existing open source software for building cloud computing platforms is necessary. This paper investigated the development of these kinds of open source software and analyzed their architec- lures from the perspective of service models. Through comparison and analysis of representatives of them, effective ways were proposed for developers to choose appropriate pieces of software to build a specific cloud computing plat- form.

Key words: Cloud computing, Open source software, IaaS, PaaS, SaaS