Amazon is arguably the first major proponent of Infrastructure as a Service (IaaS) through its Elastic Computing Cloud (EC2) service. An IaaS provider offers “raw” computing, storage, and network infrastructure so that you can load your own software, including operating systems and applications, on to this infrastructure. This scenario is equivalent to a hosting provider provisioning physical servers and storage and letting you install your own operating system, web services, and database applications over the provisioned machines. Amazon lets you rent servers with a certain CPU speed, memory, and disk capacity along with the OS and applications that you need to have installed on them (Amazon provides some “canned” software for the OS and applications known as Amazon Machine Images [AMIs], so that is one starting point). However, you can also install your own OSs (or no OS) and applications over this server infrastructure.
IaaS offers you the greatest degree of control of the three models. You need to know the resource requirements for your specific application to exploit IaaS well. Scaling and elasticity are your—not the provider’s—responsibility. In fact, it is a mini do-it-yourself data center that you have to configure to get the job done. Interestingly, Amazon uses virtualization as a critical underpinning of its EC2 service, so you actually get a virtual machine when you ask for a specific machine configuration, though VMs are not a prerequisite for IaaS. Pricing for the IaaS can be on a usage or subscription basis. CPU time, storage space, and network bandwidth (related to data movement) are some of the resources that can be billed on a usage basis.
IaaS offer many benefits to the enterprise. The benefits include
Greater financial flexibility: The service offers a hosting IT system in a highly available, service-provider-class computing environment to reduce capital expenditures on servers, software, data center space, and network equipment.
Wider choice of services: IaaS delivers services that are ubiquitously available and easily accessible, and provide well-defined service options.
Cost-effective scalability: IaaS offers a pay-as-you-go model, giving you the flexibility to scale up or down in line with business needs. Services are paid for by auditablemetered usage.
High availability: Service providers offer high availability with SLAs based on fault-tolerant technologies, helping to assure that infrastructure is available 24 hours a day, 365 days a year.
Increased security: High levels of service provider security provide a highly secure environment for applications and data.
