I. Background of Cloud Computing
Cloud computing is a computing style in which scalable and flexible IT functionalities are delivered as a service to external customers using Internet technologies. Cloud computing is not a revolutionary idea; Instead, it is an evolutionary concept that integrates various existing technologies to offer a useful new IT provisioning tool.
Cloud applications extend their accessibility through the Internet by using large data centres and powerful servers that host web applications and services. Anyone with a suitable Internet connection and a standard Internet browser can access a cloud application. Rapid evolution of cloud computing technologies can easily blur its definition perceived by the public. Yet, there are five key attributes to distinguish cloud computing from its conventional counterpart:
- Scalable and elastic
- Metered by usage
- Uses Internet technologies
Cloud computing encompasses many aspects of computing (from hardware to software) that a single solution is not able to provide all aspects. Generally speaking, cloud computing applications incorporate the combination of the following functional service models:
- Infrastructure as a Service (IaaS)
IaaS solutions provide users with physical or virtual resources that satisfy the requirements of the user applications in terms of CPU, memory, operating system and storage. Such Quality of Service (QoS) parameters are established through a Service Level Agreement (SLA) between the customer and the service provider. The end user has full controls over the virtualised computer instance, and can customise the instance accordingly. Unlike purchasing the physical servers, IaaS is usually charged on a utility basis depending on the consumption of the resources.
A big name in IaaS space is Amazon.com, which launched Elastic Compute Cloud (EC2) in 2006 to offer a pay-as-you-go hosting service for customer's computer applications. In 2008, Fujitsu also opened its "London North Data Centre" to outsource data storage and computing services with security options covering UK and International regulations, and compliance auditing according to the ISO27001 standard.