4Zhang Qi, Cheng Lu, Boutaba R. Cloud computing: state-of- the- art and research challenges [ J ]. J Intemet Serv Appl, 2010( 1 ) :7-18.
5Vaquero L, Rodero-Merino L, C aceres J, et al. A break in the clouds: towards a cloud definition [ J ]. Computer Communica-tion Review ,2009,39( 1 ) :50-55.
6Foster I,Zhao Yong, Raicu I, et al. Cloud computing and grid computing 360 - degree compared [ C ]//Proceedings of the IEEE grid computing environments workshop. Piscataway, NJ, USA : IEEE ,2008.
