The growing demand for computational power combined with the shift to cloud computing model has led to the establishment of large-scale data centers around the globe. With the increasing number of cloud deployments, the size of data centers is also increasing, thus increasing the amount of heat generated by these data centers. Consequently, cooling of the data centers becomes vital from the business and environmental perspective. Cloud computing service providers are using a number of innovative cooling strategies to beat this heat. In this paper, a systematic review has been presented for the traditional and new techniques for data center cooling. This will be of great help in the design of energy-efficient data centers.

Cloud computing is a new paradigm, where computing is delivered as a utility-based service model on a pay-as-you-go basis. Traditionally, business organizations used to invest huge amounts of capital and time in acquisition and maintenance of computational resources. Cloud computing provides a highly scalable and cost-effective infrastructure for running high performance computing, enterprise and Web applications. Cloud computing refers to the hardware, system software and applications delivered as a service over the Internet. As defined by Armbrust et al. (2009), cloud providers offer various types of services, such as Infrastructure-as-a-Service (IaaS), Platform-asa- Service (PaaS) and Software-as-a-Service (SaaS). Service providers make good use of IaaS and PaaS for developing their services without consideration of physical hardware, while users can also access on-demand and pay-per-use services anywhere in cloud computing (Rimal et al., 2009). However, the growing demand for cloud infrastructure has drastically increased the energy consumption of data centers, which has become a critical issue. High energy consumption translates to high operational cost, which reduces the profit margin of cloud providers. Hence, energy-efficient solutions are required to minimize the impact of cloud computing on the environment. In order to design such solutions, deep analysis of cloud is required with respect to its power efficiency. Data and computation are operated somewhere in a cloud, which is some collection of data center owned and maintained by third party. One of the big challenges in data centers is to manage power in the systems. Data centers consume 10 to 100 times more energy per square feet than typical office buildings (Scheihing, 2007). Moreover, cloud computing also offers enormous amount of computing power to organizations which require processing of tremendous amount of data generated almost every day. Therefore, many companies view clouds not only as a useful ondemand service, but also as a potential market opportunity.

Information Technology Journal, Cloud computing, Data centers, Cooling strategies, Energy efficiency.