Copy from :(Article) What is Cloud computing? « inZeek
I have copy because this explanation is so clear and very simple ,thanks to Chandana N. Athauda
Cloud computing is becoming a buzzword. You have heard the definition of cloud computing few times. But there are so many definitions and most of them are vendor specific. Simply cloud computing is a set of pooled computing resources and services available over the web at any given time. It mentions, computing system which are assigned through a combination of virtualized computing instances, service and software over a network. This collective of computer resources is known as “Cloud”.
Cloud computing is a computing model that provide you hardware (server and storage), software resources over the Internet. It eliminates of having to purchase, install, maintain and manage these resources locally. Instead of that, you access and use them through a Web browser or client tool based on pay as you go model.
Cloud computing is often provided infrastructures and software “as a service” over the Internet, typically in the form of infrastructure as a service (IaaS), platform as a service (PaaS), or software as a service (SaaS).
• Infrastructure as a Service (IaaS): In this model, the customers can use the hardware infrastructure; compute power, storage, and networking infrastructure as a service over the Internet (e.g., Amazon EC2, GoGrid, Rackspace)
• Platform as a Service (PaaS): In this model, the customers can create and deploy applications that developed on programming languages and tools supported by the provider. (e.g., Windows Azure, Google App Engine)
• Software as a Service (SaaS): In this model, the customers can use the provider’s applications running on cloud infrastructure. The applications can be accessed from various client tools and web browser (e.g., Salesforce.com, Microsoft Dynamics CRM and Gmail).
Cloud computing characteristics
On-demand self-service: The cloud provider has the ability to provision or auto scale computing infrastructures, such as server, storage and network without requiring human interaction.
Broad network access: The cloud network can be accessed from anywhere in globe, by using any device (e.g., smart phone, laptop, mobile devices, PDA).
Resource pooling: The cloud network provides a large pool of easily usable and accessible virtualized hardware, application, hosting technologies and services. These resources can be dynamically assigned to adjust according to the variable load and resources are typically exploited by a pay-per-use model.
Rapid Elasticity: This allows for quick scalability or downsizing of resources (scale our and scale in) on demand.
Measured service: The cloud systems robotically manage and optimize resources usage and can be monitored, controlled, and notified both the provider and customer.
Cloud computing deployment models:
Cloud computing includes different deployment models:
Public cloud deployment model is the most common deployment model and the services and infrastructure are provided off-site over the Internet. These clouds offer the greatest level of efficiency and elasticity in shared resources. And also this model is more appropriate for public or large industries. Principally, cloud infrastructures and services are owned by the provider who is selling cloud services and provider manage number of data centers around the globe.
Private cloud deployment model is operated solely for large organization and managed by the organization. It may be present on-premise or off-premise. With this model, customers can minimize the security & privacy risk; manage greatest level of data security and control. But it does not provide the elasticity and agility of public cloud services and still require to purchase and maintain infrastructures and software.
Hybrid cloud deployment model is a combination of public and private models. This approach allows a business to take advantage of the scalability and performance of public cloud computing offers and storing mission-critical data in on premises private cloud without exposing to third-party.
Community cloud deployment model is shared by several organizations. This model supports a specific community that has shared mission or interest and much similar to private cloud deployment model, but sharing same resources to store customer specific data.
How it works?
Cloud computing works by storing and processing data ‘in the cloud’ but not on your computer. The data is then transferred from local computer to cloud data centers through an Internet connection. Your data is stored on massive servers held by the provider. However, as the data is stored in the cloud, it can then be accessed from anywhere, meaning customer will never be faced with forgetting or losing data.
In a cloud computing system you shift the local computing workload into the cloud. Local computers no longer have to store or process data. The networked and virtualized cloud computing instances store and process instead. Hardware and software runs on the elastic mode as users can add or remove it at any time. The only thing the user need to do is managing the cloud computing infrastructures and services through interface software, which can be as simple as a Web browser or vendor provided client tool.
Why should you care?
Lots of businesses simply don’t have enough time, expertise or necessary financial capability to buy, deploy and manage the computing infrastructure needed to run solutions on their own. But with Cloud computing, businesses can instantly get the advantages of the computing infrastructure and services without having to purchase, implement and manage it directly.
• Cost of hardware would reduce: Easily transform existing server infrastructures into cloud environments that auto expanding and reducing server capacity on demand.
• Ease of data access: Data can be accessed at any time from multiple data centers around the globe.
• Little or no upfront costs: Cloud computing customers can avoid capital expenditure on hardware, software and services under the pay as you go model. Even customers can add additional computing infrastructures without having to pay for additional hardware.
• Eco-Friendly: Reducing the number of hardware by replacing them with cloud computing infrastructures to reduces energy costs for running hardware and cooling as well as reducing carbon dioxide emissions.
Small to medium-sized and nonprofits who have limited budget, space, and human resource can benefit financially and environmentally of using cloud computing. It saves energy, reduces the amount of hardware needed, and is often technically easier to install and maintain than in-house applications.
What to consider?
Cloud computing vendors have to put countless effort to manage all of the computing infrastructures, technologies as well as people to provide uninterrupted services. Customers trust cloud computing providers a lot as they have already stopped investing heavily in hardware, software, virtualization technologies, networking infrastructures.
There are hundreds of cloud computing providers and solutions out there. But they are not all are created equal in terms of technical architecture and business model. Customer should be smart enough to make the right choice according to the right technical and business model. Just imagine about how critical a particular service is to your business? What would happen if you couldn’t access application and data for a period of time? There are so many factors to consider before moving beyond a trial service of your cloud computer provider including reliability, security, performance, privacy, support and how well a vendor can meet them.
Basically Cloud computing vendors should provide in details explanation about their internal methodologies to protect customer data and ensure governing compliance as well as they should explain their policies such as customer decision to terminate the service or if they go out of business. If customer pays for a service, customer should also get a service level agreement (SLA) from the cloud vendor. Service Level Agreement (SLA) agreement usually contains also penalties when the requirements are not met.
Windows Azure overview
There are so many cloud computing vendors in the market. Microsoft Windows Azure is one of the leading and comprehensive Platform as a Service (PaaS) providers.
Microsoft’s Windows Azure Platform is a Microsoft cloud services operating system that provides a wide range of development, service hosting, and service management environments. Windows Azure provides on-demand compute & storage to host, scale, and manages web applications and services on the internet in Microsoft data centers.
Windows Azure runs on a large number of virtualized machines instances all accessible via the Internet. These virtualized instances provide a Windows-based environment for running applications and storing data in Microsoft global data centers.
There are three main components of Windows Azure:
1. The compute service
2. The storage service
3. The Fabric
The Windows Azure Compute service is a cloud based service that provides elastic compute volume in the cloud. It is designed to make web-scale computing based on Microsoft Windows virtualized instances as well as pure computing work. Ex: worker role is like an Ant, can help user to do background process work.
The Windows Azure storage service capable to store binary large objects (blobs), queues for integrating Windows Azure applications as well as on-premises or hosted applications and tables to store data and retrieve data via simple query language.
1. Windows Azure white papers (David Chapel)