National Institute of Standards and Technology (NIST) defines cloud computing as follows:
“Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction. This cloud model is composed of five essential characteristics, three service models, and four deployment models.”
That’s sounds like a mouthful of gibberish. Let’s break it down into pieces so we can understand it.
Cloud is just a network of data centers that you can access through the Internet. It is composed of a shared pool of configurable resources. The resources include networking, servers, memory, storage, services, and applications. These resources are available on-demand. Users can procure the resources they require by themselves without having to ask for anyone’s assistance.
Five essential characteristics
An infrastructure need five essential characteristics to be considered a cloud:
- On-Demand Access: Users can procure and release resources and services on their own without having to call anyone to setup anything for them. You get what you want, when you want it for as long as you want it.
- Broad Network Access: users can access a collection of networking tools through the Internet
- Resource Pooling: Cloud computing is composed of shared systems. Even dedicated bare metal machines procured by a customer uses shared infrastructure for electricity, networking, and physical security.
- Elasticity Rapid: Elasticity is the ability to scale up or down on demand. Scaling up means adding new resources. Scaling down means reducing the resources you use. grow or shrink, on demand.
- Pay as you go: You only pay for what you use. You don’t have to sign a big contract and pay the amount regardless of how much you use.
Service models
Cloud computing is offered in three distinctly different service model, each designed to satisfy a different set of business requirements. The service models are:
- Infrastructure as a Service (IaaS): User pay-as-you-go access to resources (CPU, memory, storage, networking) in the cloud.
- Platform as a Service (Paas): User uses the cloud to build and deliver applications. Cloud provides the underlying infrastructure.
- Software as a Service (SaaS): User delivers software and applications to its customers through the Internet. Microsoft Office 365 and Googledocs are SaaS services.
Deployment models
Deployment model defines how cloud services are delivered to its customers. There are three distinct deployment models and a fourth, which is a mix of the other three:
- Public Cloud: The resources are available to the public and data is stored on third party servers.
- Private Cloud: The resources are only available to only one customer. It is not necessarily on physically different hardware. It can simply be a virtual private cloud (VPC). A use can would be corporate Intranet.
- Community Cloud: Community cloud is a private cloud shared by a group of organizations. For example, Provincial Government can procure a community cloud that will be used by all of its ministries.
- Hybrid Cloud: Organization can mix an match different aspects of public, private, and community clouds. This is called a hybrid cloud.