What is virtualization?

 General description

Fig. 4.1/1
Fig. 4.1/1: What does it mean to virtualize?
Virtualization is a logical representation of resources not constrained by physical limitations.
Virtualization, which involves a shift in thinking from physical to logical, improves IT resource utilization by treating your company's physical resources as pools from which virtual resources can be dynamically allocated. Using virtualization in your environment, you are able to consolidate resources such as processors, storage, and networks into a virtual environment which provides the following benefits:
  1. Consolidation to reduce hardware cost.
  2. Optimization of workloads.
  3. IT flexibility and responsiveness.
Furthermore, virtual resources can have functions or features that are not available in their underlying physical resources. System virtualization creates many virtual systems within a single physical system; virtual systems are independent operating environments that use virtual resources. System virtualization is most commonly implemented with hypervisor technology; hypervisors are software or firmware components that are able to virtualize system resources. In this handbook, the author provides a round-up look at the features, deployment processes, and VM management issues for five hypervisors that help establish system virtualization within the cloud — PowerVM™, VMware ESX Server, Xen, KVM, z/VM and Hyper-V.
Fig. 4.1/2
Fig. 4.1/2: Before and after virtualization
One way of looking at virtualization is to visualize taking something large, carving it up and making it look like many small things. Think of that as partitioning an Intel server using technologies like the VMware.
Another way of looking at it is making many small things work in concert as one large thing. A good example of that is storage virtualization, where we can have multiple storage arrays from different vendors, work in concert as if they were one large single storage pool. And, finally, it’s being able to dynamically change and adjust these resources across the infrastructure. Think of that as being able to do what we could do in the mainframe for years, being able to extend that capability across a heterogeneous distributed enterprise.