In other words, you supply – and maintain – the pieces highlighted in blue in Figure 2-1.
This is the easiest and fastest migration strategy; it offers many benefits, including cost savings. But, it still means that your operations staff will need to perform tasks such as patch management, updates and upgrades.
Nevertheless, IaaS is one of the most common cloud deployment patterns to date because it reduces the time between purchasing and deployment to almost nothing. Additionally, because it is the most similar to how IT operates today, it provides an easy onboarding ramp for your current IT culture and processes. As we shall see, the bulk of migration, especially in the early phases of cloud adoption, is to IaaS.
Platform as a Service
In platform as a service (PaaS), the cloud provider maintains all system software, removing the burden of upgrades and patches from the IT department. In a PaaS deployment model (Figure 2-2), all that the enterprise needs to focus on is deploying its code on the PaaS machines; the cloud provider ensures that operating systems, database software, integration software and other features are maintained, kept up to date, and achieve a high SLA.