This is a question that has come up with a few organisations that we have been doing business with, and so we felt that it could use some clarification.
At their core, both Infrastructure as a Service (IaaS) and Platform as a Service (PaaS) are exactly the same system – they are a bundle of virtual resources hosted on our infrastructure, which is located in one of our data centres.
Where the two systems differ is in the level of control that the end client has over the infrastructure they have been allocated. With an IaaS environment the client is only given control over the application layer (the layer on which software runs) and the VM operating systems (via a console). However, this does not give the client access to deploy new machines or make changes to existing machines (other than those functions which are accesable via the OS). The other functions are managed by the provider. For instance if an IaaS client needed to scale up their capacity, they would need to contact their provider and either place a request for some additional VM’s be set up, or request an increase in the resources allocated to an existing VM.
However in a PaaS environment the client is given control over the management of their own VM’s via the hypervisor layer. For this reason, we only recommend clients opt to use PaaS if they have experience in setting up and configuring virtual servers. In this instance, if a client wished to upgrade their capacity, the client only needs to request the base resources (computing, memory, and disk) and they would be free to choose how these are allocated and configured via a web based management portal.
Hopefully that helps to clear up some of the confusion, but if you still have questions we would recommend contacting us.