Virtualization Glossary
Virtualization will bring a revolutionary approach in the way we do business and even in the way we conceive information technology today. To understand this new trend that is probably going to permanently change the world of IT, please find below some key concepts of the "virtual language".Operating System Virtualization
Unlike hardware virtualization and para-virtualization, the virtualization of Operating Systems only permits the creation of several virtual instances of an operating system on a physical system, however, it does not allow running different guest OSs.Operating System virtualization, also called OS level virtualization or shared OS virtualization, virtualizes servers on the operating system kernel level. This virtualization method forms isolated partitions or virtual environments (VE) on a single instance of physical server and operating system.
Leading vendors in this area are SWSoft with Virtuozzo, Sun with its container technology in Solaris and the new AIX from IBM that will offer virtualization in this form.
Converter
With a Converter, physical computers can be converted into virtual machines.Disaster Recovery
In virtual environments the setup of new systems and recovery of operating systems are much simpler than with standard recovery methods. There is no need to bother about adequate and special hardware, or to deal with patches and firmware.File recovery uses one single step for file encapsulation of virtual machines. This reduces the server to a set of files that can be restored on any hardware. Consequently, complete virtual machines can be replicated with replication software at a recovery location and the recovery time is reduced to a few hours.
Hardware Virtualization
This technology was the starting point of the virtualization movement. Originally, the x86-architecture did not support virtualization. Intel and ADM have refined the x86 architecture and it now supports virtualization from the hardware side.For this purpose, they implemented, among others, extensions on the processors. If the CPU runs in normal mode, the instructions are executed as usual. In the virtual mode, special CPU routines are executed, ensuring a reliable execution of virtual machines.
Hypervisor or Virtual Machine Monitor (VMM)
A hypervisor, also called virtual machine monitor, is a program that allows running several instances of one or of several different operating systems. The hypervisor is processor-specific. It controls the CPU as well as all hardware resources and provides every operating system instance with the required resources. Depending on the technology, the hypervisor emulates the hardware for every instance or translates the requirements to the CPU.High Availability
Tools like VMWare HA can, in case of a server failure, re-start virtual machines, automatically on another server. The tools also monitor the capacity of a server and choose an optimal server for the VM to run. In case of failure of the underlying physical resource, the machine is restarted, not dynamically moved, which means that there will be service downtime. This can be prevented by clustering firewalls even in virtualized network.Cloning
Virtualization permits creating running systems very fast. The conventional installation of operating systems and applications can take some time. With cloning, copies of a virtual machine can be created in a single installation and configuration process.Cloning simplifies and accelerate the distribution of standardized computing environments to employees or the creation of a base configuration for testing.
Para-virtualization
Para-virtualization is a technology initiated by the Open Source community and described as “Enlightenment” by Microsoft. A guest operating system is modified so that it executes the corresponding instructions of the hypervisor directly within a virtual machine so that no performance loss arises from the emulation of the complete hardware. The approach was originally developed at the University of Cambridge under the name Xen. Many Linux distributions have been adapted to Xen; XenSource, on the other hand, works on the para-virtualization of the Windows server of Microsoft.XenSource, Inc. was acquired by Citrix in August 2007. Xen Open Source project continues to be freely available at http://xen.org.
Snapshot
A snapshot conserves the state of a virtual machine so that it can be moved back any time to an earlier, stable system state.TCO (Total Cost of Ownership)
TCO analysis originated with the Gartner Group in 1987 and has since been developed into a number of different methodologies and software tools. A TCO assessment ideally offers a final statement reflecting not only the cost of purchase but all aspects of the further use and maintenance of the equipment, device or system.This included the costs of training support personnel and the users of the system, costs associated with failure or outage (planned and unplanned), diminished performance incidents (i.e. if users are kept waiting), costs of security breaches (in loss of reputation and recovery costs), costs of disaster preparations and recovery, floor space, electricity, development expenses, testing infrastructure and expenses, quality assurance, boot image control, marginal incremental growth, decommissioning, e-waste handling, and more.
Virtualization considerably improves TCO.
Virtual Appliance
A virtual appliance is a minimalistic virtual machine image designed to run under Parallels, VMWare, Xen, Microsoft Virtual PC, Virtual Iron or other virtualization technologies. Virtual appliances are a subset of the broader class of software appliances. Like software appliances, virtual appliances are aimed to eliminate the installation, configuration and maintenance costs associated with running complex stacks of software.A key concept that differentiates a virtual appliance from a virtual machine is that a virtual appliance is a fully pre-installed and pre-configured machine and operating system environment, whereas a virtual machine stands alone, without any application software.Typically, a virtual appliance has a web interface or an external system to configure the inner workings of the appliance. For example, StoneGate Management Center acts as an external system while StoneGate Firewall and IPS are virtual appliances.
A virtual appliance is usually built to host a single application, thus representing a new way of deploying network applications.
VSwitch, VMNIC
VSwitch stands for Virtual Switch. It represents networking entities connecting Virtual Machines in a virtual network at layer 2. VSwitch is not only fully virtual, since it can be connected to a real NIC (Network Interface Card) or NIC Team (grouping of Network Interface Cards to be used as a single NIC). VMNIC is a virtual network interface card, connecting a Virtual Machine to a VSwitch or to a Physical Team.--------------------------------------
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