Cloud

Definition

National Institute of Standards and Technology (NIST) definition:

A model for enabling convenient, on-demand network access to a shared pool of confi gurable computing resources (e.g.,networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management e ffort or service provider interaction.

More precisely...

Cloud computing offers IT resources on demand. This recent infrastructure (~2005) in the computing framework has emerged due to:
- Virtualisation everywhere (on all CPUs).
- Simple APIs (Application Programming Interface).
- Huge computing capacity of private companies: Amazon was using until 2006 half of its computing and storage capacity provided for Christmas's peak.

Characteristics

The main properties of Cloud Computing are:

  • Service on-demand.
  • Elasticity: instantiation of large number of virtual machines (theoretically infinite resources).
  • Adaptability/flexibility: choice of Operating System, CPU, memory...
  • Pool of resources.

Models

Cloud computing recovers various models:

  • Service model:

- IaaS (Infrastructure-as-a-Service): computing ressources, allows to provide virtual machine, cluster, storage and network on demand.
Ex. : StratusLab, OpenStack.
- PaaS (Plateform-as-a-Service): Web applications or environnement as batch cluster.
Ex. : Google App. Engine.
- SaaS (Software-as-a-Service): Web portals.
Ex. : Gmail.

  • Deployment model:

- Public: for all users.
- Private: users of a specific group like laboratories or consortium.
- Community: users of several specific groups.
- Hybrid

  • Economical model:

- Academic: free as StratusLab, CC-IN2P3 Cloud, FutureGrid...
- Commercial: pay-as-you-go or monthly pricing as Amazon Web Services (80 US$/month for Elastic Computing Cloud (EC2) standard instance), Google, GoGrid...
=> See a Cloud provider comparison.