"...an organization outsources the equipment used to support operations, including storage, hardware, servers and networking components...." IaaS definition from TechTarget

"You purchase technology as a service, with no capital outlay, enabling you to take a rapid path to infrastructure and application modernization at reduced risk and cost...." HP lays out the cost advantages of  its Adaptive IaaS offering.

"Raw infrastructure, such as servers and storage, is provided from the vendor premises directly as an on-demand service. Examples include Amazon Web Services, GoGrid, and Flexiscale...." Detailed discussions about IaaS and cloud Certres on CNETnews.

Infrastructure as a Service

Definition: Infrastructure as a Service (IaaS) describes one of the three main methods of accessing cloud computing based services. Organisations rent computing power and disk space and access them from desktop PCs through a private network or across the internet.



Placing IaaS in the Cloud Computing Model

IaaS has its roots in thin computing techniques that have been developing since the mid 1990s. But it was not adopted widely until virtualisation and fast, reliable and widespread internet access made it workable. Cloud computing in general refers to the idea that a company can rent space from a service provider and use it across the internet rather than having an IT infrastructure on their own premises.

There are broadly three varieties of cloud computing offerings, Software as a Service (SaaS) and Platform as a Service (Platform) being the other two. As all these services are still developing quickly the definitions and divisions between these varieties are nebulous at best and constantly shifting. There is considerable overlap in particular between IaaS and PaaS, and a service might find itself described as either of these depending on whether the description comes from a developer, system admin or a manager.

Description of IaaS

With IaaS the enterprise renting the service is likely to have considerable IT skills in-house because the infrastructure offered is quite plain. Customers select and basic software servers for their part of the cloud and then load up their libraries, applications and data then configure them themselves. Virtualisation enables IaaS providers to offer almost unlimited instances of servers to customers and make cost-effective use of the hosting hardware.

Organisations can use IaaS to quickly build new versions of applications or environments without having to order new hardware then wait for it to arrive and be configured. Another popular use of IaaS is hosting the websites of organisations. This keeps the website and its drain on IT resources away from an internal infrastructure whose primary purpose is to run the business, not the website. In these instances the IaaS provider takes on any worries about monitoring traffic and keeping the website available.

Cost Comparisons for IaaS Providers

Like most cloud computing service offerings IaaS is priced on a pay-as-you-go model, with organisations paying for the services provided from a menu. There is usually a price for the number of 'instances' of servers, either Windows or Unix, and the software environments loaded onto them such as databases or web severs, application development environments or others. Then charges are made for the amounts of data hosted and network traffic in and out of the servers.

The pricing models vary from provider to provider which makes it difficult for organisations considering a move to IaaS to compare providers against each other. The varying usage rates of different computing environments also conspire against organisations trying to compare prices. An organisation looking to outsource a high volume website might find that one provider is cheaper but that same provider may be more expensive for a company outsourcing its development environment, which would require higher computing power but much lower data transfer rates. Comparisons also need to be made between the whole cost of owning servers and storage rather than renting them from an IaaS provider.

A Real Life IaaS Provider Example

Amazon Web Services (AWS) is the most successful IaaS provider to date. Amazon has huge server farms that support the Amazon website and plenty of experience with running a reliable multiple server operation. It was decided to take the skills, technologies and hardware they had developed or acquired and offer them for hire to other organisations.

Amazon's Elastic Compute Cloud (EC2) offers, as the name suggests, server power that can grow and contract in line with an organisation's demands. Users of the service pay (at the time of going to press) ten cents (USD) per hour for the most basic server and the menu goes up from there. This offers a lot to startups or small businesses who can then afford to access server and storage capacities that would otherwise drain vital capital.

Considerations for Organisations Considering IaaS

Significant thought should be given before any organisation shifts from an internally hosted infrastructure to IaaS. The usual argument for cloud computing versus buying your own is lower costs and the removal of the IT management headache. With IaaS this is not so clear cut as you have to retain IT staff to develop and manage the software and applications that sit on top of your rented infrastructure. That has a knock on effect on the cost argument as there are fewer significant salary savings.

Other considerations for organisations considering a move to IaaS include a detailed examination of the contract and terms of service. Being tied in to any one service is a risk for businesses, as is handing over their data to someone else to look after. Contracts should be examined for tie-in periods and penalties for withdrawing early from an arrangement if it proves unsatisfactory.

Data Protection and Service Level Agreements (SLAs)

As with any other strategic partner, due diligence should be performed on the IaaS provider. Assess their financial situation and stability and examine their service level agreements to make sure they have thought about service provision and its management. Make sure also that those SLAs are backed up with hardware and network resilience and backups for data and applications.

Look closely too at the provisions for keeping data safe from theft or being compromised in some other way. This is perhaps the biggest barrier to the adoption of IaaS and other cloud computing based services, although many companies and academic research projects are working at better ways of ensuring data privacy and integrity.