Of the three major service models that cloud computing offers, Infrastructure as a Service is the most fundamental. It offers clients access to virtualized services at their most basic level. The foundation of IaaS is the virtual machine environment. When a customer purchases infrastructure services, they receive one or more virtualized environments. Clients may create and destroy virtual machines as necessary. They may also network these virtual machines together as required. The clients of an IaaS provider are exposed to a common interface. This may consist of a web portal or an Application Programing Interface (API). The billing is based on a utility computing model with the charges for the use of virtual machines being incurred by the hour or even by the minute. Beyond the virtual machine itself, IaaS providers typically enable access to storage and database services.
When an organization purchases IaaS from a provider there are many advantages. There is no need for them to purchase hardware, operating system licenses, or networking equipment. Their entire data center is outsourced and nearly all of the operation and maintenance requirements are built into the cost of the service. Organizations also look to achieve cost savings through massive efficiencies of scale. Additionally, they stand to gain flexibility and scalability that would be impossible if they were to provide their own infrastructure since additional virtual machines are created on demand and removed just as easily. IaaS is also considered to be an environmentally friendly alternative to traditional IT services. The same inherent efficiencies of scale that provide cost savings also reduce electrical consumption and other energy resources that provide heating and cooling of the data center. Finally, clients of IaaS providers can expect increased reliability as their provider will have less difficulty managing the resources to ensure redundancy and 24/7 support on a large scale than their clients would individually on a smaller scale.
As the lowest level of the three models of cloud services, IaaS places the most demands on the technical resources of the customer. Clients of an IaaS are responsible for creating and configuring the virtual machines necessary to run their applications. They are also faced with the task of developing and maintaining their own software code. Another issue is security. As with all cloud computing options, companies are reluctant to relinquish direct control of their critical infrastructure and their sensitive data. These security concerns are expected to diminish as the cloud computing model proves itself over time.