GWT Blog – GlobalWorldTech

Cloud computing is an approach to client-server in which the “server” is a dynamically scalable network of loosely coupled heterogeneous nodes that are owned by a single institution, and the “clients” are a wide variety of individuals and institutions that use fractions of shared nodes to run jobs that are transient with respect to time, compute-intensity, and storage-intensity.

Cloud services are offered at three levels, or tiers, that are distinguished by the level of abstraction that each presents to the client. Cloud computing takes that abstraction one further step. Rather than making one server appear to be several, it makes an entire data-center’s worth of servers, networking devices, systems management, security, storage and other infrastructure, look like a single computer.

1) Infrastructure-as-a-service (IaaS), which looks to the client like a dynamically scalable pool of compute and/or storage resources. The basic metered unit of IaaS is usually either a single virtual machine or an abstract storage object of a certain size. Because of the economies of scale and specialization involved, this can be to the benefit of both the business providing the infrastructure and the one using it.

2) Platform-as-a-service (PaaS), which provides API-level access to a cloud infrastructure layer. Examples of PaaS are Google AppEngine and Force.com. Because PaaS offerings often come wrapped in a vendor-specific API, the use of this layer pretty much locks you into a particular vendor.

3) Software-as-a-service (SaaS), This is the most popular tier of cloud service and it deliver’s software as a service over the Internet, eliminating the need to install and run the application on the customer’s own computer. Google Apps and Salesforce.com are the two paradigmatic SaaS examples.

The cloud represents a huge step forward in the democratization of access to compute resources. The cloud model differs from traditional outsourcers in that customers don’t hand over their own IT resources to be managed. Instead they plug into the “cloud” for infrastructure services, platform (operating system) services, or software services (such as SaaS apps), treating the “cloud” much as they would an internal data center or computer providing the same functions.