Virtualization is the act of making virtual version of a physical resource so that can be run or stored for one or more several virtual version at once. Until now the resources that have been virtualized include computer hardware platforms, storage devices, operating systems, network services, and this is still growing.
In Web Hosting, Virtualization Technology is the foundation for the growth and development for cloud computing, mostly deployed as Infrastructure as a service (IaaS), whereby virtual servers and other resources are made available to customers. In essence, This is a framework of how to regulate and utilize virtualization technology that continues to grow so that its use both on a small scale and on a massive scale remains controlled and easy to use.
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Technically, virtualization is realized by adding a piece of layer of software called the hypervisor.
Hypervisor is computer software, firmware or hardware that creates and runs virtual machines. This hypervisor functions as Virtual Machine Manager (VMM), which is an abstraction of physical hardware into virtual hardware in order to distribute the workload of all virtual machines (VMs) to each hardware proportionally.
A computer on which a hypervisor runs one or more virtual machines is called a host machine, and each virtual machine is called a guest machine. The hypervisor presents the guest operating systems with a virtual operating platform and manages the execution of the guest operating systems. Multiple instances of a variety of operating systems may share the virtualized hardware resources, for example: Linux, Windows, and macOS instances can all run on a single physical machine.
KVM stands for Kernel Virtual Machine or Kernel-based Virtual Machine. This is an open source software with a full virtualization infrastructure solution for Linux kernel that turns it into a hypervisor. It is a true core virtualization where the VPS can operates independently of the host node as its own server.
It consists of a loadable kernel module and provides the virtualization infrastructure and a processor specific module and each virtual machine has private virtualized hardware such as a network card, disk drive, graphics, etc. A wide variety of operating systems can run with KVM, including variety versions of Linux, BSD, Solaris, Windows, and other custom OS.
Xen is a type of virtualization of commercial and open source virtual machine applications. This include server virtualization, Infrastructure as a Services (IaaS), desktop virtualization, security applications, embedded and hardware appliances, and automotive / aviation. Made with the aim to run up to one hundred full featured operating systems on only one computer.
Xen Virtualization using several types of virtualization include HVM (Hardware Virtual Machine), HVM with PV drivers, PVHVM (paravirtualization with full hardware virtualization), PVH (PV in an HVM container) and PV (paravirtualization). paravirtualization technology, provides safe isolation, resource management, guarantees for quality of services and live migration for a virtual machine.
Xen HVM runs much like KVM it has better drivers for Linux based distributions. Most people select Xen for good performance with exceptional stability. Xen hosts will usually pre-allocate Ram and CPU cores to the xen hypervisor so it has its own dedicated resources that guests cannot impact on to achieve stability.
OpenVZ or OVZ stands for Open Virtuozzo. This is a virtualization solution offered by Virtuozzo company. This is also free open source operating system-level virtualization technology for Linux available under GNU GPL. It is a container style of virtualization which relies on the host node’s kernel.
OpenVZ creates multiple secure, isolated operating system instances called containers, virtual private servers (VPSs), or virtual environments (VEs) on a single physical server enabling better server utilization and ensuring that applications do not conflict. Each container runs and executes exactly like a stand-alone server.
The basic difference between KVM and OpenVZ is that OpenVZ can only host Linux OS (Operating systems), while KVM is more flexible and can host variety operating systems including many flavours and versions of Linux, Windows, and custom OS options. KVM is generally has much more stable performance than OpenVZ, while OpenVZ more cheaper than KVM.