Cloud Computing–

  • Make use of the internet
  • Maintain data and application in remote servers to be accessed by users across the globe.
  • on-demand delivery of IT resources and applications
  • using the Internet
  • pay-as-you-go pricing

Hence, it uses the computer resources that are delivered as a service over the internet.

Cloud Service Models

Figure 4: Models of cloud

Various cloud service models are

  • Infrastructure as a Service (IaaS)
  • Platform as a Service (PaaS)
  • Software as a Service (SaaS)

Infrastructure as a Service (IaaS) –

  • User accesses the physical hardware and can select as per need – CPU/storage/ etc.
  • Resource availability is managed by IaaS cloud providers.
  • Examples: Amazon CloudFormation, Rackspace Cloud, Google Compute Engine.
  • User installs operating system images with required application software.
  • Software patching and maintenance is responsibility of the user.
  • Virtual machines (VMs) run as guests by a hypervisor, like Xen or KVM with operating system, middleware, network, storage, data and applications.
  • IaaS payment depends upon resources subscribed, time used (per hour), usage of bandwidth (in gigabyte), storage(in gigabyte) or combination of any.

Platform as a Service (PaaS) –

  • Complete development platforms with development tool is provided
  • Developer builds applications without installing any tools on their computer and then deploy those applications without any specialized systems administration skills.
  • The computer and storage resources scale automatically to match application demand in PaaS.

Examples of PaaS include

  • App Engine  from Google: based on Python and Django
  • Force.com from SalesForce: based on the SalesForce SaaS infrastructure and Apex language
  • Long Jump: based on Java/Eclipse

Software as a Service –

  • Application software hosted in cloud, catering to user’s need is provided on subscription basis
  • Application is accessed via web browser by users.
  • Various business applications are provided – collaboration, CRM, ERP, invoicing, HRM, etc
  • Reduces IT costs as less hardware and software maintenance costs.
  • SaaS applications provide application customization.
  • Users not responsible for hardware or software updates
  • Example – Google Apps, Dropbox, Salesforce

Cloud Types

Various cloud type offerings depending upon level of control, are

Cloud Deployment Models

  • All-in Cloud Based Deployment – Application is fully deployed in the cloud, with all components of the application running in the cloud.
  • Hybrid Deployment – most common approach chosen and it connects infrastructure and applications between cloud-based resources and existing resources in data center.
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