Also known as a virtual machine monitor (VMM), a virtualization manager is a type of software that enables multiple operating systems to run, unmodified, on a single host computer. It is installed directly on the host computer and controls the hardware, in addition to the guest operating systems. The virtualizaton manager represents the most common implementation of virtual computer architectures. In fact, CP/CMS®, the very first virtual manager, was a time-sharing operating system (OS) developed in the 1960s by IBM, and is considered the ancestor to the company’s z/VM® OS product.
A virtualization manager creates a thin layer between the hardware and the software applications running on the virtual machine. This level of separation enables it to control how the multitude of operating systems within the virtual environment utilize the hardware resources. These resources include memory, CPUs, and network interface cards (NICs), among others. This is why the virtualization manager is often said to deliver a uniform view of the underlying hardware.
There are essentially two types of virtualization managers. The first, which is described above, is often referred to as bare-metal architecture. Type two is known as a hosted architecture. This differs from bare-metal in that it runs within an operating system, while the guest system runs above the hardware at a third level. Some of the most popular examples of this software are VMware Server™, and the open-source Linux KVM.
During the virtualization process, a virtualization manager places the OS and its applications in an isolated environment so that it can be ported and managed independently. This allows the software to map and remap virtual machines to available resources at any time, or even migrate them across multiple servers. It can also aid in balancing the load across a group of servers; to scale networks to higher capacities; and to address hardware failures. For example, if one server fails and a new one takes its place, the virtualization manager can remap the associated virtual machines accordingly. These capabilities enable it to deliver an optimal performance while improving availability and security.
The increasing interest in the high-end server hardware segment has resulted in the development of virtualization manager solutions designed for x86 instruction-set machines. X86 represents a family of instruction set architectures based on microprocessors designed by Intel®. This is the same architecture used in most personal computers (PCs), and an element that led to the development of desktop virtualization. VMware® is known as one of the first vendors to introduce software capable of virtualizing the home-based desktop PC.
A virtualization manager is the core component of virtualization technology. It is the element that facilitates partitioning of the physical hardware, and the management of the virtual machines. Virtualization managers are distributed by a number of vendors, with Microsoft®, Oracle®, and VMware® being among the most popular.