Cloud Computing

Cloud computing

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Cloud computing overview

Cloud computing is a style of computing in which dynamically scalable and often virtualised resources are provided as a service over the Internet.[1][2][3][4] Users need not have knowledge of, expertise in, or control over the technology infrastructure "in the cloud" that supports them.

The concept incorporates infrastructure as a service (IaaS), platform as a service (PaaS) and software as a service (SaaS) as well as Web 2.0 and other recent (ca. 2007–2009) technology trends that have the common theme of reliance on the Internet for satisfying the computing needs of the users. Examples of SaaS vendors include Salesforce.com and Google Apps which provide common business applications online that are accessed from a web browser, while the software and data are stored on the servers.

The term cloud is used as a metaphor for the Internet, based on how the Internet is depicted in computer network diagrams, and is an abstraction for the complex infrastructure it conceals.

Comparisons

Cloud computing is often confused with grid computing ("a form of distributed computing whereby a 'super and virtual computer' is composed of a cluster of networked, loosely-coupled computers, acting in concert to perform very large tasks"), utility computing (the "packaging of computing resources, such as computation and storage, as a metered service similar to a traditional public utility such as electricity") and autonomic computing ("computer systems capable of self-management").

Indeed many cloud computing deployments as of 2009 depend on grids, have autonomic characteristics and bill like utilities — but cloud computing can be seen as a natural next step from the grid-utility model. Some successful cloud architectures have little or no centralized infrastructure or billing systems whatsoever, including peer-to-peer networks like BitTorrent and Skype and volunteer computing like SETI@home.[citation needed]

Architecture

The majority of cloud computing infrastructure as of 2009[update] consists of reliable services delivered through data centers and built on servers with different levels of virtualization technologies. The services are accessible anywhere that has access to networking infrastructure. The Cloud appears as a single point of access for all the computing needs of consumers. Commercial offerings need to meet the quality of service requirements of customers and typically offer service level agreements.[12] Open standards are critical to the growth of cloud computing and open source software has provided the foundation for many cloud computing implementations.[13]

History

The Cloud is a term that borrows from telephony. Up until the '90s data circuits (including those that carried Internet traffic) were hard-wired between destinations. In the '90s long haul telephone companies began offering Virtual Private Network service for data communications. The telephone companies were able to offer these VPN based services with the same guaranteed bandwidth as fixed circuits at a lower cost because they maintained the ability to switch traffic to balance utilization as they saw fit, thus utilizing their overall network bandwidth more effectively. As a result of this arrangement it was thus impossible to determine in advance precisely what the path was going to be. The term "telecom cloud" was used to describe this type of networking. Cloud Computing is very similar. Cloud computing relies heavily on virtual machines (VMs) that are spawned on demand to meet the user's needs. Because these virtual instances are spawned on demand, it is impossible to determine how many such VMs are going to be running at any given time. As these VMs can be spawned on any given computer as conditions demand, they are location in-specific as well, much like a cloud network. A common depiction in network diagrams is a cloud outline.

Political issues

The Cloud spans many borders and "may be the ultimate form of globalization." As such it becomes subject to complex geopolitical issues: providers must satisfy myriad regulatory environments in order to deliver service to a global market. This dates back to the early days of the Internet, where libertarian thinkers felt that "cyberspace was a distinct place calling for laws and legal institutions of its own"; author Neal Stephenson envisaged this as a tiny island data haven called Kinakuta in his classic science-fiction novel Cryptonomicon.

Key characteristics

• Cost is greatly reduced and capital expenditure is converted to operational expenditure[33]. This lowers barriers to entry, as infrastructure is typically provided by a third-party and does not need to be purchased for one-time or infrequent intensive computing tasks. Pricing on a utility computing basis is fine-grained with usage-based options and minimal or no IT skills are required for implementation.[34]

• Device and location independence[35] enable users to access systems using a web browser regardless of their location or what device they are using, e.g., PC, mobile. As infrastructure is off-site (typically provided by a third-party) and accessed via the Internet the users can connect from anywhere.[34]

• Multi-tenancy enables sharing of resources and costs among a large pool of users, allowing for:

  • Centralization of infrastructure in areas with lower costs (such as real estate, electricity, etc.)

  • Peak-load capacity increases (users need not engineer for highest possible load-levels)

  • Utilisation and efficiency improvements for systems that are often only 10-20% utilised.[23]

• Reliability improves through the use of multiple redundant sites, which makes it suitable for business continuity and disaster recovery.[36] Nonetheless, most major cloud computing services have suffered outages and IT and business managers are able to do little when they are affected.[37][38]

• Scalability via dynamic ("on-demand") provisioning of resources on a fine-grained, self-service basis near real-time, without users having to engineer for peak loads. Performance is monitored and consistent and loosely-coupled architectures are constructed using web services as the system interface.[34]

• Security typically improves due to centralization of data, increased security-focused resources, etc., but raises concerns about loss of control over certain sensitive data. Security is often as good as or better than traditional systems, in part because providers are able to devote resources to solving security issues that many customers cannot afford. Providers typically log accesses, but accessing the audit logs themselves can be difficult or impossible.

• Sustainability comes about through improved resource utilisation, more efficient systems, and carbon neutrality. Nonetheless, computers and associated infrastructure are major consumers of energy.