Chips, compute and data centres
Cloud computing
In short
Cloud computing is on-demand access, over a network, to a shared pool of servers, storage, networks and software that can be set up and released quickly. Use is measured, and the customer need not manage every underlying machine.
- Also called
- The cloud, Cloud services
- Topic
- Chips, compute and data centres
- Level
- Beginner
- First described
- Peter Mell and Timothy Grance of NIST published Special Publication 800-145, The NIST Definition of Cloud Computing, in September 2011. They call cloud computing an evolving paradigm and offer the definition so services can be compared1.
NIST defines cloud computing as a model for ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources, such as networks, servers, storage, applications and services. Those resources can be rapidly provisioned and released with minimal management effort or service provider interaction1.
The model has five essential characteristics: on-demand self-service, broad network access, resource pooling, rapid elasticity and measured service. Resource pooling means the provider's machines serve many customers. A customer generally does not know the exact location of a resource, but may be able to specify a country, state or data centre. Measured service means use is monitored and reported, typically pay-per-use or charge-per-use1.
NIST names three service models. Software as a Service is use of the provider's applications, such as web-based email in a browser or through a program interface. Platform as a Service is deploying your own applications with the provider's languages and tools. Infrastructure as a Service is provisioning processing, storage and networks, then running your own software, including operating systems1.
The cloud is the shared pool, reached over a network. It is not a name for the internet itself. NIST calls the hardware and software underneath a cloud infrastructure: a physical layer of servers, storage and network components, and a software layer above it that provides the cloud features1. NIST's glossary publishes that same infrastructure definition2. The publication also lists four deployment models: private, community, public and hybrid1.
Example
NIST's example of Software as a Service is web-based email, opened in a browser or through a program interface. The same definition says cloud services are reached from client devices such as a mobile phone, tablet, laptop or workstation1.
Why it matters
A customer can take computing resources as demand rises and release them when it falls, and can see what was used. They generally cannot point to the exact machine, only to a broader place such as a country or a data centre1.
Questions people ask
Is cloud computing the same as online storage?
No. Storage is one resource in the shared pool. NIST's model also covers networks, servers, applications and services, offered as software, a platform or infrastructure1.
Is cloud computing always cheaper?
NIST does not say that. It says capacity can be provisioned and released as demand changes, and that measured use is typically charged per use1.
What are SaaS, PaaS and IaaS?
They are NIST's three service models. SaaS is using the provider's applications. PaaS is deploying your applications on the provider's platform. IaaS is provisioning processing, storage and networks and running your own software1.