Infrastructure as a Service (IaaS) is a cloud service model in which a provider rents you the basic building blocks of IT, such as virtual or physical servers, storage and networks, on demand and usually billed by usage. The provider owns and operates the data centers, hardware and usually the virtualization layer. You choose the operating system, install and run your applications, and manage configuration, access and data. It sits at the bottom of the cloud service stack, below Platform as a Service and Software as a Service.
At a glance
- You rent compute, storage and networking instead of buying hardware, and can usually add or remove capacity in minutes.
- The provider runs the facilities and hardware; you run the operating system, applications and data.
- Billing is commonly pay-as-you-go, with discounts for one- to three-year commitments at many providers.
- Costs grow quietly through idle servers, oversized instances, storage left behind and data transfer charges.
- It is offered by public cloud providers and also by private cloud and hosting providers.
What problem it solves
Running your own infrastructure means buying servers before you need them, waiting for delivery, finding rack space, and replacing hardware on a refresh cycle. Capacity is either short (projects wait) or excess (money sits idle). Hardware failures, power and cooling are your problem.
IaaS turns that into a rental. A team can create a server, a disk or a private network through a portal or an API and delete it when the work is done. The provider absorbs hardware failures, refresh cycles and facility costs, and spending shifts from capital purchases to an operating expense. That speed is why IaaS became the default starting point for new projects and for many data center exits.
It does not remove operations work. Someone still patches operating systems, manages backups, controls access and watches the bill. Buyers who expect IaaS to be “someone else’s problem” are often surprised by how much they still own.
How it works
Compute. Most IaaS compute is delivered as virtual machines (VMs): slices of a physical host created by the provider’s virtualization layer. You pick a size (processor cores, memory) and an operating system image. Many providers also offer bare metal servers, GPU servers and specialized instance types.
Storage. Block storage acts like a disk attached to a server; file storage provides shared folders; object storage holds large amounts of unstructured data reached over an API. Each is priced differently, and snapshots and backups are often charged separately.
Networking. You build isolated networks, subnets, firewall rules, load balancers and public IP addresses in software. Connections to your offices or data centers run over the internet (VPN) or private links.
Control and billing. Everything is managed through a web console, command-line tools and APIs, which is what makes automation and infrastructure-as-code possible. Meters record usage per resource, and the bill totals them, which is why tagging and cost reporting matter from day one.
Responsibility. Providers publish a shared responsibility model. In IaaS the customer’s share is the largest of the three service models: operating system, middleware, applications, identity, network rules and data.
If you are comparing providers, our public cloud solution page covers how to structure the evaluation.
When it matters for buyers
- When hardware is due for refresh. IaaS is one option alongside new hardware, colocation, bare metal and hybrid designs; compare all of them on full cost.
- When demand is variable or uncertain. Seasonal peaks, test environments and new products fit pay-as-you-go well.
- When a new finance leader asks about the cloud bill. Usage billing makes waste visible but only if resources are tagged and owned. Rightsizing and commitment discounts are common first steps.
- When choosing a provider. The large providers (often called hyperscalers) compete on breadth of services; smaller and private cloud providers may compete on price, support and simplicity.
- When you are deciding how much to run yourself. If your team does not want to manage operating systems, PaaS or SaaS may fit better than IaaS.
Questions to ask vendors
- Which resources are billed by usage, and what are the rates for data transfer out of your network and between regions?
- What commitment or reservation discounts do you offer, and what happens if our usage falls below the commitment?
- What does your shared responsibility model say we manage, and which managed services can take some of that on?
- What uptime commitments apply to compute and storage, and do they require us to run across multiple availability zones?
- What support tiers exist, what do they cost, and what response times do they commit to?
- How do we export our data and machine images if we leave?
- What tools do you provide for cost reporting, budgets and alerts?
How it differs from PaaS
Platform as a Service (PaaS) sits one layer up. With IaaS you get servers, disks and networks and decide what runs on them, including the operating system. With PaaS the provider also manages the operating system, runtime, scaling and often the database, and you deploy only your code and data. IaaS gives more control and works with most existing software; PaaS removes more operations work but ties your application more closely to the provider’s platform. Many organizations use both, alongside SaaS and broader cloud computing services.