Overview of cloud computing

With an on-premises datacenter you have to handle and manage everything, including purchasing and
installing the hardware, virtualization, installing the operating system and any required applications,
setting up the network (including running wires), configuring the firewall, and setting up storage for
data. Having done all that, you then become responsible for maintaining it through its entire life cycle.
This imposes both significant capital cost for the hardware and significant operational cost for its
maintenance. You do have the luxury of choosing whatever hardware and software you like—but you
also have to pay for it, regardless of whether you are using it.
Cloud computing provides a modern alternative to the traditional on-premises data center. A public
cloud vendor is completely responsible for hardware purchase and maintenance and typically provides
a wide variety of platform services that you can use. You lease whatever hardware and software
services you require on an as-needed basis, thereby converting what had been a capital expense for
hardware purchase into an operational expense. It also allows you to lease access to hardware and
software resources that would be too expensive to purchase. Although you are limited to the hardware
provided by the cloud vendor, you only have to pay for it when you use it.
Cloud environments typically provide an online portal experience, making it easy for users to
manage compute, storage, network, and application resources. For example, a user can use the portal
to create a virtual machine (VM) configuration specifying the following: the compute node size (with
regard to CPU, RAM, and local disks), the operating system, any predeployed software, the network
configuration, and the location of the node. The user then can deploy the VM based on that
configuration and within a few minutes access the deployed compute node. This quick deployment
compares favorably with the previous mechanism for deploying a VM, which could take weeks just for
the procurement cycle.
In addition to the public cloud just described, there are private and hybrid clouds. In a private cloud,
you create a cloud environment in your own datacenter and provide self-service access to compute
resources to users in your organization. This offers a simulation of a public cloud to your users, but you remain completely responsible for the purchase and maintenance of the hardware and software
services you provide. A hybrid cloud integrates public and private clouds, allowing you to host
workloads in the most appropriate location. For example, you could host a high-scale website in the
public cloud and link it to a highly secure database hosted in your private cloud (or on-premises
Microsoft provides support for public, private, and hybrid clouds. Microsoft Azure, the focus of this
book, is a public cloud. The Windows Azure Pack is a free add-on to Microsoft System Center that
allows you to host many of the core Azure services in your own data center and provide a self-service
portal experience to your users. You can integrate these into a hybrid cloud through the use of a virtual private network.

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