What is the Cloud?
Cloud Service.
A guided walk-through of the five NIST characteristics that define modern cloud computing — and the foundation for every service model covered in the rest of the CompTIA Cloud+ curriculum.
What is the Cloud?
The term "cloud computing" can be confusing. Many different offerings — with many different names — are sold by cloud service vendors. To build a common understanding, five characteristics have been agreed upon.
These characteristics, defined by the National Institute of Standards and Technology (NIST), help illustrate what cloud services are — and what they are not. Together, they form the baseline used by cloud engineers to compare, classify, and design every modern cloud offering.
You will find the remainder of this course much easier if you memorize these five characteristics quickly.
The Five Characteristics at a Glance
On-Demand
Self-Service.
Cloud consumers can provision services on an as-needed basis — without working directly with the CSP.
Resources include additional compute power, storage, new websites, or even database services. The consumer can expand or reduce these services without any human assistance from the CSP. A click, an API call, a Terraform apply — and capacity appears.
No human interaction with the provider required to scale up or down.
Broad
Network Access.
Client devices and traditional server deployments can access cloud-based resources across the network.
That network might include the local on-premises network, the public Internet, or both. Cloud resources have the potential to be globally accessible — a developer in São Paulo, a branch office in Tokyo, and an IoT sensor in Berlin can all reach the same backend.
Access from standard clients, over standard networks, from anywhere.
Resource
Pooling.
CSPs pool network, storage, and compute capabilities — then dynamically and automatically allocate them to consumers on an on-demand basis.
Consumers don't know (or care) where the resources are physically located. The next time the consumer uses those services, the resource locations may have changed. The CSP manages the resources and maximizes their use through a multi-tenant model.
Multi-tenancy. Hardware is abstracted from the consumer.
Rapid
Elasticity.
Resources are provisioned and released to adjust for changes in demand and consumption. The process may be automatic or manual.
In the traditional model, server resources are purchased as a capital expenditure — fixed in cost and capability whether used efficiently or not. With cloud, resources are dynamically allocated. Retail demand spikes during the holidays? Scale up. Quiet Tuesday in February? Scale down. Servers that would have sat idle for most of the year no longer need to be purchased or maintained.
CapEx → OpEx. Pay only for what you use, when you use it.
Measured
Service.
CSPs meter the utilization of their resources. This metering permits more efficient and dynamic resource allocation.
It also allows the CSPs to bill consumers accurately for the exact quantity of resources consumed — CPU-seconds, gigabyte-hours, request counts, egress bytes. The same telemetry that drives your invoice also drives the provider's capacity planning and the consumer's cost-optimization strategy.
Pay-per-use. Metering enables billing, alerting, and optimization.