Cloud Service Models
A cloud service model is a set of IT-related services by a cloud provider. The cloud
provider is responsible for supplying cloud-based IT resources to a cloud consumer under a
predefined mutually agreed upon service agreement (SLA). The cloud provider is responsible
for administrative maintenance and management of the cloud infrastructure, which allows the
cloud consumer to focus their administrative effort on other aspects of the business. In
essence, the cloud consumer is buying or leasing their infrastructure from the cloud provider.
The entity that legally owns the cloud service is known as the cloud service owner.
Either the cloud provider or the cloud consumer can be the cloud service owner, depending
on the terms of the SLA.
It is critical to understand who is responsible for the services hosted in the cloud.
Before an organization migrates any piece of their business to the cloud, they need to
understand who is "in control" of those resources. There are a variety of cloud service
models that offer the cloud consumer a number of different options. You will need to
understand each of the cloud service models and the service that they provide in order to
implement a successful cloud deployment. In this section you will learn each of the
different cloud service models and when to implement them.
Infrastructure as a Service (IaaS)
Infrastructure as a Service (IaaS) is the model by which the cloud consumer outsources
responsibility for their infrastructure to an external cloud provider. The cloud provider
not only owns the equipment that provides the infrastructure resources but is also
responsible for the ongoing operation and maintenance of those resources. In this model the
cloud consumer is charged on a "pay-as-you-use" or "pay-as-you-grow" basis IaaS can include
the server storage, the infrastructure, and the connectivity domains. For example, the
cloud consumer could deploy and run their own applications and operating systems, while the
IaaS provider would handle the following:
• Storage resources, including replication, backup, and archiving
• Compute resources, which are the resources traditionally provided
by servers or server farms, including processor, memory, disk, and networking
• Connectivity domains, including infrastructure management and security, such
as network load balancing and firewalls
When an organization utilizes IaaS, they no longer have to buy, maintain, or upgrade
server hardware, which can help them save resources, time, and money. Since IaaS allows an
organization to pay only for the resources they use, the company no longer needs to outlay
expenditures for hardware resources they either are not using or not using to maximum
capacity. IaaS allows an organization to spin up additional resources quickly and
efficiently without having to purchase physical hardware. For example, the IT department
might need a development environment to test a new application; with IaaS this development
environment could be spun up quickly and then removed when the new application has been
fully tested. IaaS allows an organization to meet hardware capacity spikes without having
to add resources to their data center.