Any discussion of cloud computing typically begins with virtualization. Virtualization is critical to cloud computing because it simplifies the delivery of services by providing a platform for optimizing complex IT resources in a scalable manner, which is what makes cloud computing so cost effective.
Virtualization can be applied very broadly to just about everything you can imagine including memory, networks, storage, hardware, operating systems, and applications. Virtualization has three characteristics that make it ideal for cloud computing:
Partitioning: In virtualization, you can use partitioning to support many applications and operating systems (OSes) in a single physical system.
Isolation: Because each virtual machine is isolated, each machine is protected from crashes and viruses in the other machines.
What makes virtualization so important for the cloud is that it decouples the software from the hardware.
Encapsulation: Encapsulation can protect each application so that it doesn’t interfere with other applications. Using encapsulation, a virtual machine can be represented (and even stored) as a single file, making it easy to identify and present to other applications.
To understand how virtualization helps with cloud computing, you must understand its many forms. In essence, in all cases, a resource actually emulates or imitates another resource. Here are some examples:
Virtual memory: Disks have a lot more space than memory. PCs can use virtual memory to borrow extra memory from the hard disk. Although virtual disks are slower than real memory, if managed right, the substitution works surprisingly well.
Software: There is virtualization software available that can emulate an entire computer, which means 1 computer can perform as though it were actually 20 computers. Using this kind of software you might be able to move from a data center with thousands of servers to one that supports as few as a couple of hundred.
To manage the various aspects of virtualization in cloud computing most companies use hypervisors. Because in cloud computing you need to support many different operating environments, the hypervisor becomes an ideal delivery mechanism by allowing you to show the same application on lots of different systems. Because hypervisors can load multiple operating systems, they are a very practical way of getting things virtualized quickly and efficiently.
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Source:http://www.dummies.com/how-to/content/how-to-use-virtualization-with-cloud-computing.html
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