To Grasp the Cloud—Fundamental Concepts - Deploying and Managing a Cloud Infrastructure - page 50

different OS without affecting other VMs running on the same or different server. This is
what becomes part of the platform.
All the major public cloud providers offer multiplatform support that includes support
for all the major operating systems.
Applications
Applications are completely abstracted from the underlying cloud infrastructure on which
they are deployed. The OS on which an application runs is itself abstracted from the under-
lying hardware by the hypervisor managing the VM life cycle. Some of the applications
running on the VM are there to manage other consumer-facing applications. An example of
this would be the object storage APIs implemented on top of the hypervisors. What hypervi-
sors offer is storage virtualization. Storage API applications make use of this abstraction and
implement functionality (APIs) that enable end users to consume the abstracted storage as a
service. In the case of object storage APIs, the application would be responsible for treating
units of storage as objects and exposing the functionality to push, pull, update, and delete
an object or its metadata.
Enabling Services
Software as a Service (SaaS), Platform as a Service (PaaS), and Infrastructure as a
Service (IaaS) are the primary enabling services for the cloud. The applications that run
on top of the cloud are often distributed as SaaS solutions, where subscribers pay based on
time or usage or a mixture of both.
With PaaS, cloud vendors as well as third-party developers provide vertical platforms as
a service for end users. An example of this would be an enterprise-grade content manage-
ment system (CMS) being offered as a service. This would mean that the application as
well as the cloud VMs on which it runs and the networking, storage, and bandwidth are
all accounted for and the end users would either pay per seat or based on a combination of
time and usage.
An example of an IaaS would be private cloud implementations within an enterprise.
The infrastructure is virtualized, consolidated into a single resource pool, and offered as
a service.
Services that implement the key features of any cloud, like multi-tenancy, elasticity,
abstraction, and federation, are all part of services that enable a true cloud.
Summary
Hypervisor technology is the key technology that has enabled cloud solutions. Hypervisors
virtualize compute, storage, and networking hardware and consolidate all resources avail-
able within the data center into a single resource pool. This hardware abstraction can be