Cloud computing denotes anything that involves delivering hosted services over the Internet. It utilizes the network to link the user to resources. Processing of words can be submitted to clients or users to the service provider without possession of the software or hardware. The consumer’s computer served as a basic display terminal connected to the Internet; therefore it may contain only a minimal operating system and web browser.
Cloud computing services are divided into three categories.
| Platform as a Service (PaaS) | a rental system for hardware, operating systems, storage and network capacity over the Internet, including virtualized servers and other associated services for the development of both new and existing systems
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| Infrastructure as a Service (IaaS) | a provision model, engaged on a pay-per-usage basis by the clients, in which a service provider outsources equipment to business operations while still holding responsibility in its maintenance
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| Software as a Service (SaaS) | a software distribution model in which applications are hosted by a vendor or service provider. It is made available to customers over a network, most commonly over the Internet |
Aspects of Cloud Computing
| Agility | Improves user’s ability to rapidly and inexpensively re-provision technological infrastructure resources
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| Application Programming Interface (API) | Accessibility to software that enables machines to interact with cloud software in the same way the user interface facilitates interaction between humans and computers
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| Cost | Claimed to be greatly reduced and in a public cloud delivery model capital expenditure is converted to operational expenditure. This ostensibly 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
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| Device and location independence | Enables users to access system using a web browser regardless of their location or any device they are using.
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| Multi-tenancy | Enables sharing of resources and costs across a large pool of users
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| Reliability | Improved if multiple redundant sites are used, which makes well designed cloud computing suitable for business continuity and disaster recovery
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| Scalability | Provisioning of resources on a fine-grained, self-service basis near real-time, without user having to engineer for peak loads
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| Performance | Monitored , consistent and loosely coupled architectures are constructed using web services as the system interface
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| Security | Improve due to centralization of data
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| Maintenance | Easier because they do not need to be installed on each user’s computer Easier to support and to improve as the changes reach the clients instantly
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Private cloud (also called internal cloud or corporate cloud) is a marketing term for a proprietary computing architecture. It provides hosted services to a limited number of people behind a firewall.
Due to the advances in virtualization and distributed computing, corporate network and datacenter administrators can effectively become service providers. They are able to meet the needs of their customers within the corporation.
Key Objectives of Private Cloud
Implement modular hardware that can grow and shrink dynamically, based on predetermined policies.
Workloads can be shifted dynamically and the resources devoted to a workload are dynamic and controlled by tools.
This “elasticity” is one of the most desirable aspects of private clouds.
A public cloud is based on the standard cloud computing model. It is a service provider that makes resources such as applications and storage available to the public over a network. There are 2 types of services for public cloud, ‘free’ or ‘pay-per-usage’.
The term "public cloud" differentiates the difference between the standard model and the private cloud. Standard model is a proprietary network or data center that uses ‘cloud computing technologies’ such as virtualization. A private cloud is managed by the organization it serves.
A third model, which is the called the ‘hybrid cloud’, is maintained by both internal and external providers.
References
http://bluemilecloud.com/bcloud/cloud-compute/
http://en.wikipedia.org/wiki/Cloud_computing
http://searchcloudcomputing.techtarget.com/
http://en.wikipedia.org/wiki/Cloud_computing
http://www.infoworld.com/d/cloud-computing/what-cloud-computing-really-means-031
http://searchcloudcomputing.techtarget.com/definition/public-cloud
http://searchcloudcomputing.techtarget.com/definition/private-cloud
http://en.wikipedia.org/wiki/Software_as_a_service
http://searchcloudcomputing.techtarget.com/definition/Software-as-a-Service
http://en.wikipedia.org/wiki/Platform_as_a_service
http://www.salesforce.com/paas/
http://searchcloudcomputing.techtarget.com/definition/Infrastructure-as-a-Service-IaaS
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