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1.6 INFRASTRUCTURE AS A SERVICE PROVIDERS

Public Infrastructure as a Service providers commonly offer virtual servers containing one or more CPUs, running several choices of operating systems and a customized software stack. In addition, storage space and communication facilities are often provided.

In spite of being based on a common set of features, IaaS offerings can be distinguished by the availability of specialized features that influence the cost-benefit ratio to be experienced by user applications when moved to the cloud. 

The most relevant features are: 

Geographic Presence. 

To improve availability and responsiveness, a provider of worldwide services would typically build several data centers distributed around the world. 

For example, Amazon Web Services presents the concept of “availability zones” and “regions” for its EC2 service. Availability zones are “distinct locations that are engineered to be insulated from failures in other availability zones and provide inexpensive, low-latency network connectivity to other availability zones in the same region.” Regions, in turn, “are geographically dispersed and will be in separate geographic areas or countries.”

User Interfaces and Access to Servers. 

Ideally, a public IaaS provider must provide multiple access means to its cloud, thus catering for various users and their preferences. Different types of user interfaces (UI) provide different levels of abstraction, the most common being graphical user interfaces (GUI), command-line tools (CLI), and Web service (WS) APIs.

Advance Reservation of Capacity. 

Advance reservations allow users to request for an IaaS provider to reserve resources for a specific time frame in the future, thus ensuring that cloud resources will be available at that time.

Automatic Scaling and Load Balancing. 

Applications often need to scale up and down to meet varying load conditions. Automatic scaling is a highly desirable feature of IaaS clouds. It allow users to set conditions for when they want their applications to scale up and down, based on application-specific metrics such as transactions per second, number of simultaneous users, request latency, and so forth.

Service-Level Agreement. 

Service-level agreements (SLAs) are offered by IaaS providers to express their commitment to delivery of a certain QoS. To customers it serves as a warranty. An SLA usually include availability and performance guarantees. Additionally, metrics must be agreed upon by all parties as well as penalties for violating these expectations.

Hypervisor and Operating System Choice. 

Traditionally, IaaS offerings have been based on heavily customized open-source Xen deployments. IaaS providers needed expertise in Linux, networking, virtualization, metering, resource management, and many other low-level aspects to successfully deploy and maintain their cloud offerings. 


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Case Study

  1. Amazon Web Services
  2. Flexiscale
  3. Joyent
  4. GoGrid
  5. Rackspace Cloud Servers


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