What is infrastructure as a service (IaaS)?

Infrastructure as a service (IaaS) is one of the main types of cloud computing, providing services such as compute, storage, and networking on demand and on a pay-as-you-go basis. There are two other types: PaaS (platform as a service) and SaaS (software as a service) but IaaS is the basic building block of cloud provision.

Background to IaaS

The launch of IaaS came about by accident. Amazon was looking for a way to improve the way in handle its operations, specifically an e-commerce service called Merchant. The company found that the best approach to cope with its vast number of transactions was to build a common set of infrastructure services rather than a host of separate projects.

By using this approach, Amazon realised that it had expertise in services such as compute, storage and databases. And that it could combine and run them at a large scale and low cost. The company soon realised that it could offer this service to other companies besides Amazon partners and IaaS was born.

Advantages of IaaS

There are several benefits to running IaaS within an enterprise. First and foremost, saving the cost of running and managing a data centre. That is, the capital investment in hardware and software licences, not to mention the cost of facilities (power charges) and personnel. In addition to this, by running IaaS, enterprises can save on capital expenditure by accounting for IT provision as an operating expense.

It’s not just about cost, however. By opting for IaaS, organisations have a good deal of flexibility. When they need additional services at short notice, they can burst into the cloud without provisioning a new data centre. This flexibility also means that organisations can experiment on launching new services without massive investment in new hardware and be able to do it instantly, without waiting weeks for equipment to arrive.

Disadvantages of IaaS

Despite the massive investment that providers have made in security, organisations are still wary about letting third parties hold sensitive data. Consequently many choose to hold this information within company data centres. 

There is also the issue of availability of services. There have been several instances of cloud providers’ data centres going down, sometimes for longer than a day, and that will cause massive disruption to organisations that have bet the house on these services. Businesses should negotiate tight service level agreements to ensure that cloud providers stick to their contract, but even the best SLAs can’t help when the disruption is massive.

Furthermore, when organisations wish to quit a provider, they often have considerable difficulty in extracting their data. If the provider goes bust, there are even more difficulties ahead. 

Finally, there’s the thorny problem of costs. While it’s true that users are paying on-demand for services that they actually use , this can cause problems. The very ease with which users can provision services may mean that companies over-order and pay for services they don’t need. Or, fail to shut down services once they have been used.

IaaS needs careful cost management to make it effective.

How does IaaS compare to PaaS and SaaS?

Since Amazon semi-accidentally gave birth to IaaS, and our modern concept of what cloud computing is, the service has been joined by many other *aaS options. The graphic above summarises them well.

You may also find our guides to the public cloud, hybrid cloud and multicloud useful. Or check out our cloud computing section, which includes an article about how cloud computing is changing football at every level.

Maxwell Cooter
Maxwell Cooter

Although Max trained to be a programmer, he quickly found his vocation in journalism. He was the founder editor of Cloud Pro, the UK's first dedicated cloud publication and has written for dozens of titles, including The Guardian and The Daily Telegraph. At TechFinitive he writes about cloud computing and data.