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What Is IaaS? IaaS vs PaaS vs SaaS

IaaS delivers servers, storage and network as a service; the operating system and above stay with you. How it differs from PaaS and SaaS, and who owns what.

Oğuzhan Gerçek··7 min read
What Is IaaS? IaaS vs PaaS vs SaaS

Short answer: IaaS (Infrastructure as a Service) means getting basic infrastructure, such as servers, storage and network, from a provider as a service. You don't buy hardware; you pay for the capacity you use, while the operating system, applications and data remain your responsibility. With PaaS the provider also runs the platform, and with SaaS it runs the application itself. The real difference between the three is where responsibility changes hands.

What is IaaS?

The definition of cloud computing still in use today comes from SP 800-145, published by the US National Institute of Standards and Technology (NIST) in 2011. In NIST's words, IaaS lets the consumer provision processing, storage, networks and other fundamental computing resources. The consumer can run any software on them, including operating systems; it does not manage the physical infrastructure underneath, but it controls the operating system, storage and the applications it deploys.

In practice, an IaaS service is built from these blocks:

  • Virtual servers: Virtual machines you create by choosing CPU, memory and disk capacity.
  • Storage: Block storage attached to a server as a disk, and object storage for backups and archives.
  • Network: Virtual networks, firewall rules, load balancers and connectivity to the outside world.

NIST looks for five characteristics before calling a service cloud: on-demand self-service, broad network access, resource pooling across many consumers, rapid elasticity and measured service. A physical server rented in a provider's data center is therefore not IaaS on its own; those five characteristics are what separate IaaS from classic hosting.

IaaS vs PaaS vs SaaS

Think of the three models as steps on the same ladder. At each step the provider takes on one more layer:

  • IaaS: The provider runs the hardware, the virtualization layer and the network. The operating system, middleware, application and data are yours. Examples: virtual servers, block and object storage.
  • PaaS (Platform as a Service): The provider also runs the operating system and the platform the application runs on. You bring only your application and your data. Examples: managed databases (DBaaS) and application platforms.
  • SaaS (Software as a Service): The application itself is the service. What remains with you is user settings and the data. Examples: email, CRM, office suites. More in our SaaS article.

The choice is less a technology decision than a control decision. With IaaS you make every call, from the operating system version to the patch schedule; with SaaS most of those calls belong to the provider. More control means more operational work.

The shared responsibility model: who owns what?

Cloud providers spell out how responsibility is split. AWS sums up its shared responsibility model this way: the provider secures the cloud itself, and the customer secures what it puts in the cloud. On IaaS-class virtual servers, patching the operating system and configuring security are the customer's job.

Microsoft's version follows the same logic: moving from IaaS to PaaS to SaaS, the provider's share grows. But some responsibilities never change hands in any model: data, endpoints, user accounts and access management always stay with the customer.

In practice, however well the provider protects its data center, an unpatched server or an account with excessive permissions is a gap in your layer. That is why a written list of who does what matters when you sign an IaaS contract.

When does IaaS make sense?

IaaS is not the right answer for every workload. It pays off best in these cases:

  • Variable demand: Loads that multiply during campaigns or at month-end. Adding and removing capacity as needed is cheaper than buying hardware for the peak.
  • Fast starts: Test and development systems, short-lived projects. A hardware order takes weeks; a virtual server is up in minutes.
  • Leaving the hardware cycle: Handing server refreshes, warranty tracking and spare parts to the provider.

It makes less sense for steady, predictable workloads that consume a lot of resources. These often come out cheaper on your own hardware or in colocation. Then there is unused capacity: in Flexera's 2026 report, organizations estimate that 29% of their IaaS and PaaS spend is wasted, and the figure rose for the first time in five years. We cover how to get the bill under control in our FinOps article.

How big is the IaaS market?

According to Gartner's forecast of August 10, 2026, worldwide IaaS spending will grow 29.3% in 2026 to reach $287.3 billion, up from $222.2 billion in 2025. About a third of the growth comes from infrastructure optimized for AI: that line grows 96.4% to $42.3 billion.

IaaS is not the largest slice of cloud spending. IDC's March 2026 forecast puts public cloud spending above $1 trillion in 2026, with SaaS making up more than half of it.

Data residency when choosing IaaS in Türkiye

In Türkiye, an IaaS decision also has a legal side. If your virtual server runs in a region abroad, the personal data on it counts as transferred abroad, and the conditions in Article 9 of the KVKK (Türkiye's personal data protection law), amended as of June 1, 2024, apply. You can find the details in our article on KVKK and cross-border transfers.

The rules are stricter for banks: BDDK regulation treats cloud services as outsourcing and limits which cloud models can be used, which we cover in our BDDK article. The need is growing worldwide too: Gartner expects sovereign cloud IaaS spending to rise 35.6% to $80.4 billion in 2026. We discuss the control plane side of the topic in our sovereign cloud article.

IaaS vs managed cloud

With IaaS you get the resources and keep the operations. Who monitors the server, who patches it, who tests that the backup actually restores, who responds when a disk fills up at 3 a.m.? The IaaS contract does not answer those questions.

Managed cloud fills that gap: operation of the operating system and the work around it is added on top of the infrastructure. Monitoring, patching, backup and incident response move to the provider, and where responsibility ends is again written into the contract. For organizations that cannot staff a 24/7 infrastructure on-call rotation themselves, it is the middle path between buying IaaS alone and building a full operations team.

Frequently asked questions

What does IaaS mean? Infrastructure as a Service: getting server, storage and network resources from a provider on a usage basis instead of buying them.

What are examples of IaaS? Virtual servers, block and object storage, virtual networks and load balancers. AWS EC2, Azure Virtual Machines and Google Compute Engine are well-known examples; virtual server services delivered from data centers in Türkiye follow the same model.

What is the difference between PaaS and IaaS? With IaaS, the operating system and everything above it are your responsibility. With PaaS the provider also manages the operating system and the runtime platform; you bring only your application and data.

What is SaaS? Software as a Service: using an application over the internet as a service, with nothing to install. Email, CRM and office suites are the most common examples.

Is IaaS secure? Security of the infrastructure layer sits with the provider; the operating system, access management, configuration and data sit with you. Security therefore depends as much on how your layer is run as on the provider's infrastructure.

Is a cloud server an IaaS service? Yes. A cloud server is the best-known example of the model: a virtual server where you choose CPU, memory and disk capacity and pay for what you use.

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