“ Virtualization ” 29 1. Introduction 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 designed to run a single operating system and a single application. This leaves most machines vastly underutilized. Virtualization lets you run multiple virtual machines on a single physical machine, sharing the resources of that single computer across multiple environments. Different virtual machines can run different operating systems and multiple applications on the same physical computer. Virtualization is a framework or methodology of dividing the resources of a computer into multiple execution environments, by applying one or more concepts or technologies such as hardware and software partitioning, time-sharing, partial or complete machine simulation, emulation, quality of service, and many others. Virtualization is technology for supporting execution of computer program code, from applications to entire operating systems, in a software-controlled environment. Such a Virtual Machine (VM) environment abstracts available system resources (memory, storage, CPU core(s), I/O, etc.) and presents them in a regular fashion, such that “guest” software cannot distinguish VM-based execution from running on bare physical hardware. Fig (1): Virtual Machine Virtualization commonly refers to native virtualization, where the VM platform and the guest software target the same microprocessor instruction set and comparable system architectures. Virtualization can also involve execution of guest software cross-compiled for a NEHRU COLLEGE OF ENGINNERING AND RESEARCH CENTRE “ Virtualization ” 29 different instruction set or CPU architecture; such emulation or simulation environments help developers bring up new processors and cross-debug embedded hardware. A virtual machine provides a software environment that allows software to run on bare hardware. This environment is created by a virtual-machine monitor, also known as a hypervisor. A virtual machine is an efficient, isolated duplicate of the real machine. The hypervisor presents an interface that looks like hardware to the “guest” operating system. It allows multiple operating system instances to run concurrently on a single computer; it is a means of separating hardware from a single operating system. it can control the guests’ use of CPU, memory, and storage, even allowing a guest OS to migrate from one machine to another. It is also a method of partitioning one physical server computer into multiple “virtual” servers, giving each the appearance and capabilities of running on its own dedicated machine. Each virtual server functions as a full-fledged server and can be independently rebooted. How Does Virtualization Work? Virtualization platform 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. Each virtual machine contains a complete system, eliminating potential conflicts. Virtualization works by inserting a thin layer of software directly on the computer hardware or on a host operating system. This contains a virtual machine monitor or “hypervisor” that allocates hardware resources dynamically and transparently. Multiple operating systems run concurrently on a single physical computer and share hardware resources with each other. By encapsulating an entire machine, including CPU, memory, operating system, and network devices, a virtual machine is completely compatible with all standard x86 operating systems, applications, and device drivers. You can safely run several operating systems and applications at the same time on a single computer, with each having access to the resources it needs when it needs them. NEHRU COLLEGE OF ENGINNERING AND RESEARCH CENTRE “ Virtualization ” 29 Virtual Machine Fig(2): VMware 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. Virtual Machines Benefits Virtual machines possess four key characteristics that benefit the user: • Compatibility: Virtual machines are compatible with all standard x86 computers • Isolation: Virtual machines are isolated from each other as if physically separated • Encapsulation: Virtual machines encapsulate a complete computing environment • Hardware independence: Virtual machines run independently of underlying hardware NEHRU COLLEGE OF ENGINNERING AND RESEARCH CENTRE “ Virtualization ” 29 Virtual Infrastructure A virtual infrastructure lets you share your physical resources of multiple machines across your entire infrastructure. A virtual machine lets you share the resources of a single physical computer across multiple virtual machines for maximum efficiency. Resources are shared across multiple virtual machines and applications. This resource optimization drives greater flexibility in the organization and results in lower capital and operational costs. Fig(3): Virtual Infrastructure A virtual infrastructure consists of the following components: • Bare-metal hypervisors to enable full virtualization of each x86 computer. • Virtual infrastructure services such as resource management and consolidated backup to optimize available resources among virtual machines Virtual Infrastructure Benefits Delivering built–in availability, security and scalability to applications. It supports a wide range of operating system and application environments, as well as networking and storage infrastructure. NEHRU COLLEGE OF ENGINNERING AND RESEARCH CENTRE “ Virtualization ” 29 2. History of Virtualization Virtualization is a proven concept that was first developed in the 1960s by IBM as a way to logically partition large, mainframe hardware into separate virtual machines. These partitions allowed mainframes to "multitask"; run multiple applications and processes at the same time. Virtualization was effectively abandoned during the 1980s and 1990s when client-server applications and inexpensive x86 servers and desktops established the model of distributed computing. The growth in x86 server and desktop deployments has introduced new IT infrastructure and operational challenges. These challenges include: • Low Infrastructure Utilization - Typical x86 server deployments achieve an average utilization of only 10% to 15% of total capacity. Organizations typically run one application per server to avoid the risk of vulnerabilities in one application affecting the availability of another application on the same server. • Increasing Physical Infrastructure Costs - The operational costs to support growing physical infrastructure have steadily increased. Most computing infrastructure must remain operational at all times, resulting in power consumption, cooling and facilities costs that do not vary with utilization levels. • Increasing IT Management Costs - As computing environments become more complex, the level of specialized education and experience required for infrastructure management personnel and the associated costs of such personnel have increased. Organizations spend disproportionate time and resources on manual tasks associated with server maintenance, and thus require more personnel to complete these tasks. • Insufficient Failover and Disaster Protection - Organizations are increasingly affected by the downtime of critical server applications and inaccessibility of critical end user desktops. The threat of security attacks, natural disasters, health pandemics and terrorism has elevated the importance of business continuity planning for both desktops and servers. NEHRU COLLEGE OF ENGINNERING AND RESEARCH CENTRE “ Virtualization ” 29 • High Maintenance end-user desktops - Managing and securing enterprise desktops present numerous challenges. Controlling a distributed desktop environment and enforcing management, access and security policies without impairing users' ability to work effectively is complex and expensive. Present Day Today, computers based on x86 architecture are faced with the same problems of rigidity and underutilization that mainframes faced in the 1960s. 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. Why Virtualization: A List of Reasons Following are some reasons for and benefits of virtualization: . Virtual machines can be used to consolidate the workloads of several under-utilized servers to fewer machines, perhaps a single machine (server consolidation). Related benefits are savings on hardware, environmental costs, management,