By David Postlethwaite

Cloud Service Models

There are three main service models in the cloud. You will see these buzz words being used a lot in cloud discussions:

• IaaS   - Infrastructure as a Service
• PaaS  Platform as a Service
• SaaS  Software as a Service

To get a better understanding what these mean take a look at this diagram which shows the typical layers of an IT Solution
Starting from network to application

IaaS - Infrastructure as a Service

Think of Infrastructure as a Service as Hardware to Rent. Instead of purchasing network equipment, storage space or servers you use the cloud provider’s infrastructure.
This means the cloud provider owns and maintains the housing, running and maintaining of all the hardware, not you. You will need to install the operating system and database software but you don’t have to worry about maintaining the hardware. And the cloud provider will have mechanisms in place to ensure that your hardware continues to work in the event of a failure

PaaS - Platform as a Service

Platform as a Service can be thought of as Servers to Rent. Here the cloud provider supplies you with hardware, operating system and database server. You simply place your data in the database server and connect your application to it. You do not have to worry about patching, upgrades, failover and backups. The Cloud provider will manage all that for you. With both IaaS and PaaS you have the flexibility to use more or less storage or processing power as and when you require it.
This is attractive to business which might otherwise have to maintain large amounts of storage space just for occasional peak times.

SaaS Software as a Service

With Software as a service we go whole way and simply rent applications over the Internet from the Vendor. We don’t have to worry about hardware , operating systems or software maintenance. You only have to pay for the time that you use the application on a “pay-as-you-go” basis which is why this is sometimes called “software on demand”. As well as removing the need to buy, install and manage software on your computer, it also has the advantage of the software being accessible from anywhere with an internet connection.