Cloud computing has taken the IT industry by storm. It has ushered a new era of computing and IT delivery model. This chapter introduces terms and terminologies associated with cloud computing from a vendor neutral perspective. Readers are gradually introduced to cloud computing elements which pave the way for better understanding in later chapters.
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There is a plethora of definitions available for cloud computing. Many different sources have defined cloud computing from different perspective and the definitions have been the subject of debate. We will present several definitions in this section and will unfold cloud computing with detailed description of its traits and features. Cloud computing has attracted attentions from academia, industries, tech-savvy individuals and analytic firms. This positive attitude and rumination towards cloud computing resulted in many definitions.
Cloud has often been used as a metaphor for internet. In network diagram blocks of network and transport mechanism are often represented by a cloud (Rittinghouse & Ransome, 2010). However, cloud computing has got some additional new meanings. To start with, it can be stated that cloud computing is the culmination of grid computing, utility computing, unified communication (UC), Service Oriented Architecture (SOA), Web 2.0 and many other similar technologies. It has been described as the new age of computing, adopting a “pay as you go” or utility model, similar to electricity, water and other common place utilities. To an end user, cloud computing is an illusion of a pool of infinite computing resources on demand. These resources are served by a sprawl of servers, networking equipments and storage systems from a data center. This new consumption and delivery model displays a shift from a Capital Expenditure (CAPEX) to an Operating Expenditure (OPEX).
From the myriads of definitions available, the definition by National Institute of Standards and Technology (NIST) has been widely accepted (NIST, 2010).
Cloud computing is a model for enabling convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction.
Cloud computing is an elastically scalable, virtualized system which can be rapidly provisioned with flexible pricing model (pay as you go) (Rimal, Eunmi, & Lumb, 2009; Sarna, 2011).
According to Reliable Adaptive Distributed Systems Laboratory, UC Berkeley, cloud computing is the aggregation of application delivered as services over internet and hardware and systems software in the datacenters that provide those services (Armbrust, et al., 2009).