Virtual Machine Migration

Virtual machines are becoming more common with the evolution of virtualization technology. Virtual machines are often created to perform certain tasks that are different than tasks performed in a host environment.

Virtual machines are implemented by software emulation methods or hardware virtualization techniques. Depending on their use and level of correspondence to any physical computer, virtual machines can be divided into two categories:

• System Virtual Machines: A system platform that supports the sharing of the host computer's physical resources between multiple virtual machines, each running with its own copy of the operating system. The virtualization technique is provided by a software layer known as a hypervisor, which can run either on bare hardware or on top of an operating system.
• Process Virtual Machine: Designed to provide a platform-independent programming environment that masks the information of the underlying hardware or operating system and allows program execution to take place in the same way on any given platform.

Some of the advantages of a virtual machine include:

• Allows multiple operating system environments on a single physical computer without any intervention
• Virtual machines are widely available and are easy to manage and maintain.
• Offers application provisioning and disaster recovery options

Some of the drawbacks of virtual machines include:

• They are not as efficient as a physical computer because the hardware resources are distributed in an indirect way.
• Multiple VMs running on a single physical machine can deliver unstable performance

Virtual machine configuration primarily defines the overall operational specification of a virtual machine. Generally, virtual machine configuration is designed to meet the underlying requirements and capacity of the host physical machine. It is assigned with justifiable resources that can be scaled on run time by the hypervisor. Virtual machine configuration attributes include but are not limited to:

• CPU allocation and settings
• Memory allocation and settings
• Storage allocation and settings
• Peripheral device settings ( CD-ROM, floppy, etc.)
• Boot order settings
• Communication adapter and ports settings ( serial port, parallel port, USB, network adapter, etc.)
• System startup and shutdown
• Other administrative settings

Virtual Machine Migration (VM Migration)

In hardware virtualization, physical hardware pieces are carved up into a set of virtual machines — logical hardware pieces that do not have a physical shell or composition, which are essentially just programmed pieces of an overall hardware system. In a virtualization setup, a central hypervisor or another tool allocates resources like CPU and memory to virtual machines. For instance, in older networks, most of the individual elements were physical workstations, such as desktop PCs, which were connected by Ethernet cabling or other physical connections. By contrast, virtual machines do not have a physical interface. They do not have a box or shell or anything to move around. But they can be connected to the same keyboards, monitors and peripherals that humans have always used to interact with personal computers.

Virtual Machine Migration. In virtual machine migration, system administrators move these virtual pieces between physical servers or other hardware pieces. In an effort to facilitate this, a new kind of migration has evolved called "live virtual machine migration." Live migration involves moving these virtual machines without shutting down a client system. Modern services often provide live migration functionality to make it easier to move virtual machines without doing a lot of other administrative work.