Contents 1 Cloud computing 1 1.1 Overview ............................................... 1 1.2 History of cloud computing ...................................... 1 1.2.1 Origin of the term ....................................... 2 1.2.2 The 1950s ........................................... 2 1.2.3 The 1990s ........................................... 2 1.3 Similar concepts ............................................ 3 1.4 Characteristics ............................................. 3 1.5 Service models ............................................ 4 1.5.1 Infrastructure as a service (IaaS) ............................... 5 1.5.2 Platform as a service (PaaS) ................................. 5 1.5.3 Software as a service (SaaS) ................................. 5 1.6 Cloud clients .............................................. 5 1.7 Deployment models .......................................... 6 1.7.1 Private cloud ......................................... 6 1.7.2 Public cloud .......................................... 6 1.7.3 Hybrid cloud ......................................... 6 1.7.4 Others ............................................. 7 1.8 Architecture .............................................. 7 1.8.1 Cloud engineering ....................................... 7 1.9 Security and privacy .......................................... 7 1.10 The future ............................................... 8 1.11 The cloud revolution is underway ................................... 8 1.12 See also ................................................ 8 1.13 References ............................................... 9 1.14 External links ............................................. 11 2 Platform as a service 12 2.1 Development and uses ......................................... 12 2.2 Advantages and disadvantages ..................................... 13 2.3 Types ................................................. 13 2.3.1 Public, private and hybrid ................................... 13 2.3.2 Mobile PaaS ......................................... 13 i ii CONTENTS 2.3.3 Open PaaS .......................................... 13 2.3.4 PaaS for Rapid Development ................................. 13 2.3.5 System types ......................................... 13 2.4 Providers ............................................... 14 2.5 See also ................................................ 14 2.6 References .............................................. 14 3 Software as a service 16 3.1 History ................................................. 16 3.2 Distribution .............................................. 17 3.3 Pricing ................................................ 17 3.4 Architecture .............................................. 17 3.5 Characteristics ............................................. 17 3.5.1 Configuration and customization ............................... 17 3.5.2 Accelerated feature delivery .................................. 18 3.5.3 Open integration protocols .................................. 18 3.5.4 Collaborative (and “social”) functionality ........................... 18 3.6 Adoption drivers ............................................ 18 3.7 Adoption challenges .......................................... 19 3.8 Emerging trends ............................................ 19 3.9 Data escrow .............................................. 19 3.10 Criticism ................................................ 19 3.11 See also ................................................ 20 3.12 References ............................................... 20 3.13 Text and image sources, contributors, and licenses .......................... 22 3.13.1 Text .............................................. 22 3.13.2 Images ............................................ 25 3.13.3 Content license ........................................ 25 Chapter 1 Cloud computing sources to users. For example, a cloud computer facil- ity that serves European users during European business Servers hours with a specific application (e.g., email) may real- locate the same resources to serve North American users Laptops Application Desktops during North America’s business hours with a different 60 50 70 40 80 7 8 30 90 6 F E 5 100 4 20 3 10 110 2 0 120 1 0 12345 application (e.g., a web server). This approach should NEWS Monitoring Collaboration Finance Content Communication maximize the use of computing power thus reducing en- Platform vironmental damage as well since less power, air condi- tioning, rack space, etc. are required for a variety of func- Identity Queue Object Storage Runtime Database tions. With cloud computing, multiple users can access Infrastructure a single server to retrieve and update their data without purchasing licenses for different applications. Compute Network Block Storage Phones Tablets The term “moving to cloud” also refers to an organiza- tion moving away from a traditional CAPEX model (buy Cloud Computing the dedicated hardware and depreciate it over a period of time) to the OPEX model (use a shared cloud infrastruc- Cloud computing metaphor: For a user, the network elements ture and pay as one uses it). representing the provider-rendered services are invisible, as if ob- Proponents claim that cloud computing allows compa- scured by a cloud. nies to avoid upfront infrastructure costs, and focus on projects that differentiate their businesses instead of on Cloud computing is a computing term or metaphor infrastructure.[4] Proponents also claim that cloud com- that evolved in the late 1900s, based on utility and con- puting allows enterprises to get their applications up and sumption of computer resources. Cloud computing in- running faster, with improved manageability and less volves deploying groups of remote servers and software maintenance, and enables IT to more rapidly adjust re- networks that allow different kinds of data sources to be sources to meet fluctuating and unpredictable business uploaded for real time processing to generate computing demand.[4][5][6] Cloud providers typically use a “pay as results without the need to store processed data on the lo- you go” model. This can lead to unexpectedly high cal machine. Clouds can be classified as public, private charges if administrators do not adapt to the cloud pricing or hybrid.[1][2] model.[7] The present availability of high-capacity networks, low- cost computers and storage devices as well as the 1.1 Overview widespread adoption of hardware virtualization, service- oriented architecture, and autonomic and utility com- [8][9][10] [3] puting have led to a growth in cloud computing. Cloud computing relies on sharing of resources to Companies can scale up as computing needs increase and achieve coherence and economies of scale, similar to a then scale down again as demands decrease utility (like the electricity grid) over a network.[2] At the foundation of cloud computing is the broader concept of Cloud vendors are experiencing growth rates of 50% per converged infrastructure and shared services. annum.[11] Cloud computing, or in simpler shorthand just “the cloud”, also focuses on maximizing the effectiveness of the shared resources. Cloud resources are usually not only shared by multiple users but are also dynamically 1.2 History of cloud computing reallocated per demand. This can work for allocating re- 1 2 CHAPTER 1. CLOUD COMPUTING 1.2.1 Origin of the term cuits, began offering virtual private network (VPN) ser- vices with comparable quality of service, but at a lower The origin of the term cloud computing is unclear. The cost. By switching traffic as they saw fit to balance server expression cloud is commonly used in science to describe use, they could use overall network bandwidth more ef- a large agglomeration of objects that visually appear from fectively. They began to use the cloud symbol to denote a distance as a cloud and describes any set of things whose the demarcation point between what the provider was re- details are not inspected further in a given context.[12] An- sponsible for and what users were responsible for. Cloud other explanation is that the old programs to draw net- computing extends this boundary to cover all servers as work schematics surrounded the icons for servers with a well as the network infrastructure.[19] circle, and a cluster of servers in a network diagram had [13] As computers became more prevalent, scientists and several overlapping circles, which resembled a cloud. technologists explored ways to make large-scale com- In analogy to above usage the word cloud was used as puting power available to more users through time- a metaphor for the Internet and a standardized cloud- sharing. They experimented with algorithms to optimize like shape was used to denote a network on telephony the infrastructure, platform, and applications to prioritize schematics and later to depict the Internet in computer CPUs and increase efficiency for end users.[20] network diagrams. With this simplification, the implica- Since 2000 cloud computing has come into existence. In tion is that the specifics of how the end points of a net- early 2008, OpenNebula, enhanced in the RESERVOIR work are connected are not relevant for the purposes of European Commission-funded project, became the first understanding the diagram. The cloud symbol was used [14][15] open-source software for deploying private and hybrid to represent the Internet as early as 1994, in which clouds, and for the federation of clouds.[21] In the same servers were then shown connected to, but external to, the year,