Cloud Service Models


A cloud service model is a set of IT-related services by a cloud provider. The cloud provider is responsible for supplying cloud-based IT resources to a cloud consumer under a predefined mutually agreed upon service agreement (SLA). The cloud provider is responsible for administrative maintenance and management of the cloud infrastructure, which allows the cloud consumer to focus their administrative effort on other aspects of the business. In essence, the cloud consumer is buying or leasing their infrastructure from the cloud provider.

The entity that legally owns the cloud service is known as the cloud service owner. Either the cloud provider or the cloud consumer can be the cloud service owner, depending on the terms of the SLA.

It is critical to understand who is responsible for the services hosted in the cloud. Before an organization migrates any piece of their business to the cloud, they need to understand who is "in control" of those resources. There are a variety of cloud service models that offer the cloud consumer a number of different options. You will need to understand each of the cloud service models and the service that they provide in order to implement a successful cloud deployment. In this section you will learn each of the different cloud service models and when to implement them.

Infrastructure as a Service (IaaS)

Infrastructure as a Service (IaaS) is the model by which the cloud consumer outsources responsibility for their infrastructure to an external cloud provider. The cloud provider not only owns the equipment that provides the infrastructure resources but is also responsible for the ongoing operation and maintenance of those resources. In this model the cloud consumer is charged on a "pay-as-you-use" or "pay-as-you-grow" basis IaaS can include the server storage, the infrastructure, and the connectivity domains. For example, the cloud consumer could deploy and run their own applications and operating systems, while the IaaS provider would handle the following:

Storage resources, including replication, backup, and archiving
Compute resources, which are the resources traditionally provided by servers or server farms, including processor, memory, disk, and networking
Connectivity domains, including infrastructure management and security, such as network load balancing and firewalls

When an organization utilizes IaaS, they no longer have to buy, maintain, or upgrade server hardware, which can help them save resources, time, and money. Since IaaS allows an organization to pay only for the resources they use, the company no longer needs to outlay expenditures for hardware resources they either are not using or not using to maximum capacity. IaaS allows an organization to spin up additional resources quickly and efficiently without having to purchase physical hardware. For example, the IT department might need a development environment to test a new application; with IaaS this development environment could be spun up quickly and then removed when the new application has been fully tested. IaaS allows an organization to meet hardware capacity spikes without having to add resources to their data center.

Platform as a Service (PaaS)

Platform as a Service (PaaS) enables customers to deploy applications without assuming the capital and resource costs that they would be obligated to pay if they had to purchase and maintain their own infrastructure. Instead, consumers either purchase or create applications of services that are available exclusively over the Internet. In addition to an infrastructure, these users also have access to both tools and programming languages that are required to create PaaS applications through their cloud provider via an API, or application programming interface.

Because PaaS providers do not need to worry about configuring or maintaining an infrastructure for development, they are able to focus on what really matters to them: application development. This focus allows them to get design changes to market much faster than they would in a traditional environment, where they would need to split focus between their infrastructure and the code development itself.

Software as a Service (SaaS)

Sotfware as a Service (SaaS) is a cloud service model that allows a cloud consumer to take advantage of a software delivery model that provides on-demand applications over the Internet using a web browser. Like other cloud service models, SaaS is hosted at a cloud provider so the cloud consumer does not need to purchase the hardware required to deploy and operate the application. When an organization deploys SaaS, they no longer have to manage the installation or the infrastructure that supports the application hosted at the cloud providers. SaaS provides an efficient method for organizations to deploy line-of-business applications such as customer relationship management (CRM) and accounting.

Database as a Service (DBaaS)

Database as a Service (DBaaS) is essentially a form of software specializing in delivery of database operations. This service enables cloud providers to offer database functionality to multiple, discrete cloud consumers. DBaaS infrastructures support the following competencies:

Self-service provisioning for the customer of database instances
Monitoring of attributes and quality-of service levels to ensure compliance with provider-defined agreements
Carefully measured usage of database services, enabling charge back functionality for each individual cloud consumer

A DBaaS infrastructure may also support service elasticity, secure multitenancy, access using a wide range of devices, automated resource management, and capacity planning.

Communications as a Service (CaaS)

Communications as a Service (CaaS) is a cloud service model that enables an organization to use communications services in the cloud by using a cloud provider to access voice over IP (VoIP), instant messaging (IM), private branch exchange (PBX), CaaS allows an organization to deploy only the communication service that they need without the cost of the hardware or having to manage the communications infrastructure, allowing for significant cost savings for the organization.

Business Process as a Service (BPaaS)

Business Process as a Service (BPaaS) represents the penetration of the cloud model beyond the conventional technical IT service into the process of the business itself. BPaaS is the combination of business process step execution monitoring with one of the primary cloud models: IaaS, PaaS, or SaaS. Business process monitoring is the evaluation of a set of business activities to provide feedback on the progress of the defined steps within that process. The purpose of business monitoring is to optimize the delivery of business services by analyzing which steps are completed efficiently and which steps fail on a regular basis, and to take appropriate actions for improving the process based on that analysis. The systems that handle this step execution monitoring are referred to as business process management systems (BPMS).

When using BPaaS, the activities of these traditional business process management systems are uploaded to a cloud service that performs each of the steps in the process and then monitors the execution of each step. The advantage of BPaaS as opposed to a traditional BPMS is similar to other cloud model benefits; it gives its customers the flexibility of a pay-per-use model and reduces their cost of entry by eliminating the need to purchase and build an infrastructure to support it.

Anything as a Service (XaaS)

Anything as a Service (XaaS) is the delivery of IT as a service through hibrid cloud computing; it works with one or a combination of software as a Service (SaaS), Infrastructure as a Service (IaaS), Platform as a Service (PaaS), Communications as a Service, Database as a Service (DBaaS), and%frasl;or Business as a Service (BPaaS). With XaaS the X is a variable that can be changed to represent a variety of different cloud services. XaaS is simply a term used to describe the distribution of different IT components within the cloud model.

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