Cloud services are usually grouped into three models: Infrastructure, Platform and Software as a Service. Comparing IaaS vs PaaS vs SaaS comes down to one question: how much of the stack do you manage, and how much does the provider manage for you?
Before you start
- No setup needed. Reading what virtualization is helps, because virtualization sits underneath most cloud services.
The responsibility stack
| Layer | On-premises | IaaS | PaaS | SaaS |
|---|---|---|---|---|
| Application and data | You | You | You | Provider (you own the data) |
| Runtime, middleware | You | You | Provider | Provider |
| Operating system | You | You | Provider | Provider |
| Virtualization, servers, storage, network | You | Provider | Provider | Provider |
IaaS: Infrastructure as a Service
You rent virtual machines, block storage and networks, and manage everything from the OS up.
- Examples: cloud VMs, a KVM VPS, object and block storage.
- Pros: full control, any software, root access.
- Cons: you handle updates, security and backups. See how a VPS works.
PaaS: Platform as a Service
You deploy code; the provider runs the servers, OS and runtime.
- Examples: app platforms that build from Git, managed databases, serverless functions.
- Pros: fast deployments, autoscaling, less operations work.
- Cons: less control, platform-specific limits, possible lock-in.
SaaS: Software as a Service
You use a finished application in the browser or through an API.
- Examples: webmail, CRM, office suites, helpdesk tools.
- Pros: nothing to install or maintain.
- Cons: least customisation; you depend on the vendor's features and data policies.
Where web hosting fits
Shared cPanel hosting sits between PaaS and SaaS: the provider runs the servers, PHP, databases and email, and you upload your site. MdmHost's web hosting includes LiteSpeed, free SSL and daily backups, so you manage only your website. A VPS is IaaS.
How to choose
- Need a ready tool: SaaS.
- Want to ship code without managing servers: PaaS or managed hosting.
- Need custom software, special OS settings or full control: IaaS.
Frequently asked questions
Is a VPS IaaS?
Yes. You get a virtual machine with root access and manage the software yourself.
Is serverless PaaS?
It is usually counted as PaaS, sometimes called FaaS (Function as a Service).
Can I combine models?
Most businesses do, for example SaaS email, PaaS databases and IaaS servers for custom apps.