Comparison of Cloud Service Models

This comparison has been done on the basis of the services that are provided by each type of model, its Service Level Coverage and the customization flexibility for the different types of consumers.

	SaaS	PaaS	IaaS
Consumers	End Users	Application Owners	·      Application Owner or IT provides OS ·      Middleware ·      Application support
Services Provided	Finished applications	·      Runtime environment for application ·      Cloud Storage ·      Other Cloud Services such as Integration	·      Virtual Server ·      Cloud Storage
Service Level Coverage	·     Application uptime ·     Application performance	·      Environment availability ·      Environment Performance ·      No application coverage	·      Virtual Server Availability ·      Time to provision ·      No Platform or Application
Customizations	·     Flexibility from minimal to no customization ·     Capabilities dictated by market or providers	·      High degree of application level customization available within constraints of the service offered ·      Many applications will need to be rewritten	·      Minimal Constraints on applications installed on standardized virtual OS builds

by : software company India

Platform As a Service (PaaS)

Platform as a service (PaaS) is a category of cloud computing services that provides a computing platform and a solution stack as a service. In this model, the consumer creates an application or service using libraries or/and tools from the provider. The consumer also controls configuration settings and software deployment. The provider provides the servers, networks, storage, and other services that are required to host the customer's application.

Platform Aa a Service offerings facilitate the deployment of services and/or applications without the cost and complexity of managing and buying the underlying software, hardware and provisioning hosting capabilities. All "as-a-service" offerings are characterized as providing low initial cost, self-service, incremental cost as your service usage grows, best practices built-in, resource sharing, management services, automated deployment, lifecycle management, reuse. PaaS provides these capabilities for application and service development.

Figure - Platform As a Service. Source - http://goo.gl/97hmwq

There are various types of PaaS service providers; however, all offer deployment environment and application hosting, along with various integrated services. Services offer varying levels of scalability and maintenance.

PaaS offerings might also include facilities for application development, application design, testing, and deployment as well as services such as web service integration, team collaboration, and marshalling, database integration, scalability, storage, security, persistence, application versioning, application instrumentation, state management, and developer community facilitation.

Besides the service engineering aspects, PaaS offerings cover mechanisms for service management, such as monitoring, discover, workflow management, reservation etc.

Example:

Figure 2 - SaaS, PaaS and IaaS Example. Source - http://goo.gl/FJliOe

Reference: Software company India

Infrastructure As a Service

NIST defines Infrastructure as a service (IaaS) as “The capability provided to the consumer is to provision processing, networks, storage and other fundamental computing resources where the consumer is able to deploy and run arbitrary software, which can include operating systems and applications. The consumer does not control or manage the underlying cloud infrastructure but has control over storage, operating systems and deployed applications; and possibly limited control of selected networking components (e.g., host firewalls).”. The following figure shows the cloud computing layers:

Figure 1 Cloud deployment models

In the most basic cloud-service model, providers of IaaS offer computers – physical or (more often) virtual machines – and other resources. (A hypervisor, such as Xen, OpenStack, Oracle VirtualBox, VMware ESX/ESXi, KVM or Hyper-V runs the virtual machines as guests. Pools of hypervisors within the cloud operational support, system can support large numbers of virtual machines and the ability to scale services down and up according to customers' varying requirements.) IaaS clouds often offer various additional resources such as a virtual-machine disk image library, and file or object storage, firewalls, raw block storage, load balancers, IP addresses, virtual local area networks (VLANs), and software bundles. IaaS cloud providers supply these resources on-demand from their large pools installed in data centers. For wide-area connectivity, customers can use either the carrier clouds (dedicated virtual private networks) or Internet. Lately, this paradigm has been extended towards actuation and sensing resources, with an aim to provide virtual actuators and sensors as a services SAaaS.

To install and deploy their applications, cloud users install operating-system images and their application software on the cloud infrastructure. In this model, the cloud user maintains and patches the operating systems and the application software. Cloud providers typically charge IaaS services on a utility computing basis; cost reflects the amount of resources consumed and allocated. Software company India

Cloud communications and cloud telephony, rather than replacing local computing infrastructure, replace local telecommunications infrastructure with Voice over IP and other off-site Internet services.

Ref : software company in India