A Cloud Definition

Nota:

• Clouds are a large pool of easily usable and accessible virtualised resources (such as hardware, development platforms and/or services). These resources can by dynamically reconfigured to adjust to a variable load (scale), allowing for an optimum resource utilisation. This pool of resources is typically exploited by a pay-per-use model in which guarantees are offered by the Infrastructure Provider by means of customised SLAs.

1. Shift of computing infrastructure to networks
   1. Reduces costs associated with management of hardware and software.
   2. Outsourcing of hosting and computing resources
2. Actors
   1. Service Providers (SPs) makes services available to Service Users.
   2. Infrastructure as a Service (IaaS)

      Nota:

      • IPs manage a large set of computing resources, such as storing and processing capacity. Through virtualisation, they are able to split, assign and dynamically resize these resources to build ad-hoc systems as demanded by customers. They deploy the software stacks that run their services.
   3. Platform as a Service (PaaS)

      Nota:

      • Cloud systems can offer an additional abstraction level: instead of supplying virtualised infrastructure, they can provide the software platform where systems run on. The sizing of the hardware resources demanded by the execution of the services is made in an a transparent manner.
   4. Software as a Service (SaaS)

      Nota:

      • There are services of potential interest to a wide variety of users hosted in Cloud systems. This is an an alternative to locally run applications. An example of this is the only alternative of typical office applications such as word processors.
3. A Definition
   1. Immediate scalability and resources usage optimisation
      1. Provided by increasing monitoring and automation of resources management
   2. Business Model through reduction of costs
      1. User friendliness
   3. Utility Computing
      1. Pay for computing power