IaaS, SaaS and DRaaS: What They Are and When to Use Each
A short guide to the three cloud service models people ask about most, who manages what in each one, and how to pick the right fit for your business.
· 2 min read · DomestiCloud Team
When a company starts moving to the cloud, three terms come up almost immediately: IaaS, SaaS and DRaaS. All three are cloud services, but they answer different needs. Knowing the difference helps you buy what you actually need rather than what you hear about most.
IaaS: renting infrastructure
Infrastructure as a Service gives you virtual servers, storage and networking that you rent as you use them. The provider looks after the hardware, power, cooling and virtualisation. You still look after the operating system, the applications and the data on top.
IaaS fits when you:
- have your own applications to move off physical servers,
- need capacity that grows and shrinks with load,
- want full control over the operating system and its configuration.
SaaS: using a finished application
Software as a Service is a ready-made application you reach through a browser or a client app, such as company email or a collaboration suite. The provider runs everything, from the servers to application updates. You only manage your users and your data.
SaaS fits when the need is common and requires little customisation. It is the fastest to start with, and also the one with the least room to change how the application works.
DRaaS: a standby for when the main site fails
Disaster Recovery as a Service provides a standby site in the cloud that keeps receiving a replica of your systems. If the primary data center has an outage, services fail over to that standby site.
Two numbers shape any DRaaS design:
- RTO (Recovery Time Objective): how long a system may stay down before it has to be running again.
- RPO (Recovery Point Objective): how much recent data you can afford to lose, measured in time.
The smaller those numbers, the more often replication has to run and the more it costs. That is why not every system needs the same target.
Who manages what
| Layer | IaaS | SaaS | DRaaS |
|---|---|---|---|
| Hardware and network | Provider | Provider | Provider |
| Operating system | You | Provider | Same as the source system |
| Application | You | Provider | Same as the source system |
| Data and user access | You | You | You |
One thing never moves: your data and who can access it stay your responsibility in every model.
How to choose
- List the systems you run and mark the ones a ready-made application could replace. Those are SaaS candidates.
- Systems you need to keep control of are IaaS candidates.
- For every important system, set its RTO and RPO. Systems that cannot stay down for long need DRaaS.
In practice the three are often used together: email on SaaS, core applications on IaaS, and DRaaS protecting both.
Want to talk through your company's cloud needs? Reach our team at sales@domesticloud.com.