What do you mean by cloud? Describe about the basic characteristics of cloud.

 Cloud

The “cloud” in cloud computing can be defined as the set of hardware, networks, storage, services, and interfaces that combine to deliver aspects of computing as a service. Cloud services include the delivery of software, infrastructure, and storage over the Internet. A cloud service is any service made available to users on demand via the Internet from a cloud computing provider's servers as opposed to being provided from a company's own premises servers explained before, the most common cloud service is that one offers data storage disks and virtual servers, i.e. infrastructure. Examples of Infrastructure-as-a-Service (IaaS) companies are Amazon, Rackspace, and Flexi scale. Cloud computing is the use of computing resources (hardware and software) that are delivered as a service over a network (typically the Internet). 

Cloud computing is the on-demand availability of computer system resources, especially data storage (cloud storage) and computing power, without direct active management by the user. Large clouds often have functions distributed over multiple locations, each location being a data center. Cloud computing relies on sharing of resources to achieve coherence and typically uses a "pay-as-you-go" model which can help in reducing capital expenses but may also lead to unexpected operating expenses for unaware users.

Characteristics/Advantages  of Cloud Computing

• Service Oriented:

The defining characteristic of cloud computing is the service-oriented feature. All the IT-related services are hosted in cloud infrastructure. Companies should not have to buy expensive servers, and network equipment and invest in expensive manpower. All they need is to subscribe to any cloud service provider and get what they want. In this way, we can decrease our capital expenditure and move to operate via Operating expenditure.

• Broad Network Access:

Cloud Capabilities are available over the network and accessed through standard mechanisms that promote use by heterogeneous thin or thick client platforms such as mobile phones, laptops and PDAs.

• On Demand:

A consumer can provision computing capabilities, such as server processing and network storage, as needed automatically without requiring human interaction with each service provider. computer services such as email, applications, network, or server services can be provided without requiring human interaction with each service provider. Cloud service providers providing on-demand self-services include Amazon Web Services (AWS), Microsoft Google, IBM, and Salesforce.com.

• Reliability, Elasticity, and scalability:

The cloud is reliable in the sense that the infrastructure setup for the cloud is robust and backed up for high availability. It is a resilient replicating and backup strategy that is targeted at a huge customer base. The cloud is elastic, meaning that resource allocation can get bigger or smaller depending on demand. Elasticity enables scalability, which means that the cloud can scale upward for peak demand and downward for lighter demand. Scalability also means that an application can scale when adding users and when application requirements change.

• Resource Pooling (Processor, Memory, and Storage):

Cloud infrastructure should have features of resource pooling i.e. resources (CPU, Memory, Disk) should be categorized in a hierarchy as per the need of computing. Resource pooling is mainly used for utilizing servers up to their potential. Since most of the ties server resources are unused, we can use the concept of virtualization to pool its resources.

• Measured Service (Pay per Use):

Cloud computing resource usage can be measured, controlled, and reported providing transparency for both the provider and consumer of the utilized service. Cloud computing services use a metering capability that enables control and optimize resource use. This implies that just like air tie, electricity, or municipality water IT services are charged per usage metrics – pay per use. The more you utilize the higher the bill. Just as utility companies sell power to subscribers, and telephone companies sell voice and data services, IT services such as network security management, data center hosting or even departmental billing can now be easily delivered as a contractual service.

• Multi-Tenancy:

Multi-tenancy refers to a principle in IT infrastructure where a single instance of the software runs on a server, serving multiple client organizations (tenants). With a multitenant architecture, a software application is designed to virtually parting its data and configuration, and each client organization works with a customized virtual application instance. Each customer does its own work without interfering with other customers even though they are hosted on the same platform.