New Delhi, Aug 1 (IANS): Amazon was the top infrastructure as a service (IaaS) vendor in 2017 as the IaaS Public Cloud Services market grew 29.5 per cent in the year to hit $23.5 billion -- up from $18.2 billion in 2016, Gartner said on Wednesday.

Amazon was followed by Microsoft, Alibaba, Google and IBM.

IaaS is an instant computing infrastructure, provisioned and managed over the Internet. It is one of the three main categories of Cloud computing services -- software as a service (SaaS) and platform as a service (PaaS).

"The top four providers have strong IaaS offerings and saw healthy growth as IaaS adoption is being fully embraced by mainstream organisations and as Cloud availability expands into new regions and countries," said Sid Nag, Research Director at Gartner.

Amazon was the leader in the IaaS Public Cloud market with an estimated $12.2 billion revenue in 2017 -- up 25 per cent from 2016.

Microsoft was second with growth of more than 98 per cent on its IaaS offering, with revenue surpassing $3.1 billion in 2017.

At third, Alibaba's 2017 growth of 63 per cent reflected the company's successful investment in research and development (R&D).

The top four providers -- Amazon, Microsoft, Alibaba and Google -- represent approximately 73 per cent of the total IaaS market, and 47 per cent of the combined IaaS and infrastructure utility services (IUS) market.

"Cloud-directed IT spending now constitutes more than 20 per cent of the total IT budget for organisations using cloud. Many of these organisations are now using Cloud to support production environments and business-critical operations," added Nag.