From the Computer Utility to Cloud Computing - To the Cloud: Big Data in a Turbulent World - page 41

Public cloud . This model is typically provided by large cloud-services
businesses, such as Amazon Web Services, and offers software, platforms,
and infrastructure to the general public or to an industry association. In
essence the public cloud is available to anyone who can pay for it and it
is expected to grow ive times faster than overall IT-industry expansion
through 2016 (Lee 2013b). Public cloud SaaS conigurations are the most
widely known because they include familiar services like Google's Gmail,
Apple's iCloud, and the marketing services provided by Salesforce. Orga-
nizations that require the greater control but prefer to stay in the public
cloud might opt for a PaaS system like Microsoft's Azure or Google's
App Engine. Those needing still more control turn to IaaS public-cloud
services like those provided by Amazon and Terremark.
Hybrid cloud . When the cloud infrastructure is composed of both public
and private clouds that remain unique entities but are linked by technology
that allows for data and application portability, we refer to a hybrid cloud
service. Many organizations have divided requirements that might lead
them to seek out the public cloud for most of their needs and a private
cloud coniguration to maintain the security of sensitive data. Hybrid-
cloud providers who share ownership and management with their customer
organizations enable them to enjoy the beneits of both types of deploy-
ments. While hybrid clouds appear to be an excellent choice because they
can be all things to their customers, they also require careful management
to balance the component cloud formations. The company Rackspace has
become a leader in the hybrid model.
Community cloud . This model brings together several organizations that
have common interests, such as a similar organizational mission, similar
set of regulatory requirements, security needs, compliance expectations, or
policies. One or more of these organizations might manage the cloud or,
what is more frequently the case, they may together hire a third party who
runs the cloud in the data center of one of the organizations or houses it
off-site. For example, a group of airlines might build a community cloud
to house a common reservation system. Community clouds are chosen
because they can be customized to meet the speciic needs of an organi-
zational group, such as a collection of media irms interested in sharing
ile-based digital media content. Community clouds are also interesting