- Hosting all of a physical machine's hardware and software components independently on a single or shared hardware resource.
- In virtualization, we can run multiple operating systems on a single machine at the same time. In the case of dual-boot, we can run an OS at a time.
- Virtual Machine: VM is the set of virtual hardware devices, virtual RAM and virtual CPU that run like a traditional operating system.
- Virtual Server: It is also a virtual machine running as a server. It can run one or possibly more server-based application. This server may be a database or messaging or anything else.
- VMM (Virtual Machine Monitor): VMM consists of multiple virtual machines top of the hypervisor to handle all the VMs.
- Hypervisor: Hypervisor consists of multiple VMs and communicates with the real hardware to provide the resources to the available virtual machines. It controls all the physical resources on the computer. two types of the hypervisor exist as shown in the below diagram.
- VIM (Virtual Infrastructure Management): VIM is a tool that is used for managing multiple VMMs. openNebula is the open-source VIM available. Using the VIM tool, we can manage the multiple VMMs from single computer or console.
- Microsoft Hyper-V: This is a type 2 hypervisor. It supports live migration of virtual machines without any downtime. It has the ability of VM snapshots or checkpoints, So in case of any disaster or failure, user can roll back the VM configuration to the time when it was working fine.
- Citrix XenServer: This is a type 1 hypervisor, so it can run directly on hardware. This improves the overall system utilization and increases application performance because it accesses the hardware directly.
- XenServer automatically balances the load among all the virtual machines. If any virtual machine is idle then Xenserver dynamically allocates the memory to the another VM(s) that need more resources.
- There is improved security, administration and delegated access in terms of the management
- It supports live migration and site recovery services.
- It supports dynamic load balancing.