Understanding Infrastructure as a Service

Infrastructure as a Service (IaaS) is the delivery of computer hardware (servers, networking technology, storage, and data center space) as a service. It may also include the delivery of operating systems and virtualization technology to manage the resources.

The IaaS customer rents computing resources instead of buying and installing them in their own data center. The service is typically paid for on a usage basis. The service may include dynamic scaling so that if the customer winds up needing more resources than expected, he can get them immediately (probably up to a given limit).

Dynamic scaling as applied to infrastructure means that the infrastructure can be automatically scaled up or down, based on the requirements of the application.

Additionally, the arrangement involves an agreed-upon service level. The service level states what the provider has agreed to deliver in terms of availability and response to demand. It might, for example, specify that the resources will be available 99.999 percent of the time and that more resources will be provided dynamically if greater than 80 percent of any given resource is being used.

Currently, the most high-profile IaaS operation is Amazon’s Elastic Compute Cloud (Amazon EC2). It provides a Web interface that allows customers to access virtual machines. EC2 offers scalability under the user’s control with the user paying for resources by the hour. The use of the term elastic in the naming of Amazon’s EC2 is significant. The elasticity refers to the ability that EC2 users have to easily increase or decrease the infrastructure resources assigned to meet their needs. The user needs to initiate a request, so this service provided isn’t dynamically scalable. Users of EC2 can request the use of any operating system as long as the developer does all the work. Amazon itself supports a more limited number of operating systems (Linux, Solaris, and Windows). For an up-to-the-minute description of this service, go to http://aws.amazon.com/ec2.

Companies with research-intensive projects are a natural fit for IaaS. Cloudbased computing services allow scientific and medical researchers to perform testing and analysis at levels that aren’t possible without additional access to computing infrastructure.

Other organizations with similar needs for additional computing resources may boost their own data centers by renting the computer hardware — appropriate allocations of servers, networking technology, storage, and data center space — as a service. Instead of laying out the capital expenditure for the maximum amount of resources to cover their highest level of demand, they purchase computing power when they need it.

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