XaaS (anything-as-a-service) is any kind of service provided over the internet using cloud computing. The "X" in this acronym stands in for any variable: XaaS is an umbrella term for things like infrastructure-as-a-service (IaaS), platform-as-a-service (PaaS), software-as-a-service (SaaS) etc.

At its core, XaaS an outsourcing framework somewhat similar to the carsharing model. Driving a "car-as-a-service" means that the client is only charged for actually using a vehicle. There is no need for a client to buy and to insure a car, to subject it to technical inspections, or to pay for parking. This mode of transportation is easily available with minimal investment – you pay as you go. Once you park the car in a designated area, it is no longer your liability.

IT services can operate according to the same kind of model: clients bear no capital costs and only pay for actual use of a service. Instead of building and maintaining a physical data centre, they lease one virtually from a provider.

The IaaS framework delivers infrastructure as an online service. Companies that need to set up data storage and cloud access have to have a certain amount of infrastructure: adequate server and network equipment, premises (either a server room or a dedicated data centre), and staff to set up and maintain it. Organising infrastructure in-house takes considerable time and money; in the context of some security requirements, it could even be impossible.

To reduce cost, businesses may rent data centre space in which to install their servers – a colocation model. Another solution would be hosting – the rental of a vendor’s physical server. A third option is hiring a specific amount of computing capacity – processor cores, computer memory, storage space and so on. This third approach exactly what IaaS is about.

The main difference between IaaS and traditional hosting services is the ability