What is Virtualization?
Virtualization is a proven software technology that is rapidly transforming the IT landscape and fundamentally changing the way that people compute.Today’s powerful x86 computer hardware was originally designed to run only a single operating system and a single application, but virtualization breaks that bond, making it possible to run multiple operating systems and multiple applications on the same computer at the same time, increasing the utilization and flexibility of hardware
How Does Virtualization Work?
In essence, virtualization lets you transform hardware into software. Use software such as VMware ESXi to transform or “virtualize” the hardware resources of an x86-based computer—including the CPU, RAM, hard disk and network controller—to create a fully functional virtual machine that can run its own operating system and applications just like a “real” computer.
Multiple virtual machines share hardware resources without interfering with each other so that you can safely run several operating systems and applications at the same time on a single computer.
The VMware approach to virtualization inserts a thin layer of software directly on the computer hardware or on a host operating system. This software layer creates virtual machines and contains a virtual machine monitor or “hypervisor” that allocates hardware resources dynamically and transparently so that multiple operating systems can run concurrently on a single physical computer without even knowing it.
However, virtualizing a single physical computer is just the beginning. VMware offers a robust virtualization platform that can scale across hundreds of interconnected physical computers and storage devices to form an entire virtual infrastructure.
What is a Virtual Machine?
A virtual machine is a tightly isolated software container that can run its own operating systems and applications as if it were a physical computer. A virtual machine behaves exactly like a physical computer and contains it own virtual (ie, software-based) CPU, RAM hard disk and network interface card (NIC).
An operating system can’t tell the difference between a virtual machine and a physical machine, nor can applications or other computers on a network. Even the virtual machine thinks it is a “real” computer. Nevertheless, a virtual machine is composed entirely of software and contains no hardware components whatsoever. As a result, virtual machines offer a number of distinct advantages over physical hardware
Compatibility
Just like a physical computer, a virtual machine hosts its own guest operating system and applications, and has all the components found in a physical computer (motherboard, VGA card, network card controller, etc). As a result, virtual machines are completely compatible with all standard x86 operating systems, applications and device drivers, so you can use a virtual machine to run all the same software that you would run on a physical x86 computer.
Isolation
While virtual machines can share the physical resources of a single computer, they remain completely isolated from each other as if they were separate physical machines. If, for example, there are four virtual machines on a single physical server and one of the virtual machines crashes, the other three virtual machines remain available. Isolation is an important reason why the availability and security of applications running in a virtual environment is far superior to applications running in a traditional, non-virtualized system.
Encapsulation
A virtual machine is essentially a software container that bundles or “encapsulates” a complete set of virtual hardware resources, as well as an operating system and all
its applications, inside a software package. Encapsulation makes virtual machines incredibly portable and easy to manage. For example, you can move and copy a virtual machine from one location to another just like any other software file, or save a virtual machine on any standard data storage medium, from a pocket-sized USB flash memory card to an enterprise storage area networks (SANs).
Hardware Independence
Virtual machines are completely independent from their underlying physical hardware. For example, you can configure a virtual machine with virtual components (eg, CPU, network card, SCSI controller) that are completely different from the physical components that are present on the underlying hardware. Virtual machines on the same physical server can even run different kinds of operating systems (Windows, Linux, etc).
When coupled with the properties of encapsulation and compatibility, hardware independence gives you the freedom to move a virtual machine from one type of x86 computer to another without making any changes to the device drivers, operating system, or applications. Hardware independence also means that you can run a heterogeneous mixture of operating systems and applications on a single physical computer.
