Column Data centers Private clouds are also used when the customer is geographically diverse and wishes to centralize and optimize their technology needs so that it is accessible from any of their physical locations, which in turn allows for more efficient use of technology resources. Public and private clouds represent the two black and white extremes of cloud models, but there are many www.info.hotims.com/44637-28 90 ASHRAE JouRnAl ashrae.org O ct O b e r 2 0 1 3 shades of grey within a given business and that has led to many businesses adopting the following model: Hybrid Cloud. Since the applications of any one business can have different levels of security or confidentiality, the businesses themselves may opt for delineating the applications such that some exist on a public cloud and others exist on a more secure and dedicated private cloud. The private cloud may be owned and operated by the business or outsourced to a third-party private cloud provider. One particular type of hybrid cloud arrangement has emerged as the cloud models continue to evolve and adapt to the emerging market. For businesses that are in some way related to each other, a cloud model to consider is: Community Cloud. An attempt to receive the cost benefits of a shared tenancy of a public cloud with the security and control provided by a private cloud have led to multiple businesses with similar concerns and needs using a single private cloud infrastructure. Again, the physical infrastructure of the cloud can be local or remote to the businesses that it supports, and its ownership can be one or more of the supported businesses or a third party. Community clouds are potential solutions for entities that have some common bond. For example, community clouds can be used by different departments within a large corporation or governmental entity even if the actual work being performed by these different departments was independent of each other. Other examples could include parent companies of many subsidiaries sharing a community cloud or strategic alliances/partnerships between independent companies sharing a community cloud.