Cloud computing
The delivery of services over the internet. Also defined as a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources that can be rapidly provisioned and released with minimal management effort or service provider interaction. Usually includes several common infrastructure used in information technology, including but not limited to:
- virtual machines (compute power);
- storage;
- database; and
- other resources.
# Terminologies
| Term | Definition |
|---|---|
| Availability | Accessible when needed |
| Tolerance | Ability to withstand a certain amount of failure and remain functional |
| Scalability | Ability to easily grow in size, capacity, or scope when required, usually based on demand |
| Elasticity | Ability to scale when required and to reduce when resources are no longer required |
# Characteristics
Cloud computing has several notable characteristics compared to on-premises computing, including:
- on-demand usage (self-service on demand);
- ubiquitous access (broad network access);
- multitenancy (resource pooling);
- elasticity (rapid expansion);
- measured usage; and
- resiliency.
# Models
# Cloud computing models
There are three cloud computing models often adopted:
- infrastructure-as-a-service (IaaS): users manage servers, operating systems, and network infrastructure;
- platform-as-a-service (PaaS): users create and run applications; the infrastructure is managed by the cloud provider;
- software-as-a-service (SaaS): users only run the applications; the application is managed by the cloud provider
# Cloud deployment models
There are also three cloud deployment models often adopted:
- all-in-cloud: applications are fully deployed in the cloud, and all parts of the applications run in the cloud;
- hybrid: an organisation’s infrastructure into the cloud is extended while also connected to an internal system;
- on-premises/private cloud: applications are run in a cloud infrastructure from an organisation’s own data centre.
# Benefits
Cloud computing mainly aims to move businesses from managing their own hardware to using hardware maintained by a third-party only whenever they need it. In general, cloud computing:
- allows for less capital expenses (expenses) and more operational expenses;
- allows companies to enjoy massive economies of scale;
- allows accurate capacity planning;
- increases speed and agility;
- focuses IT resources to meeting business needs; and
- allows for the deployment of IT resources globally.