XEN Hypervisor
The XEN hypervisor is an open source hypervisor used for virtual machine management. It thus enables a hardware level virtualization and is installed on top of the bare-metal hardware. Therefore this hypervisor technology implements the approach of native virtual machines and is one concrete underlying tool to handle big data on large servers. It was created by Cambridge University but is used world-wide also in commercial environments today. Examples of XEN-based commercial solutions are Citrix XenServer or Oracle VM.
This hypervisor tool can be used to virtualize machines with host CPUs like x86, x86-64, or IA-64 for example. These host CPUs typically run a host operating system such as Linux, Solaris, or even NetBSD. But with the XEN Hypervisor the physical machines can be virtualized and run other guest operating systems like Windows XP, Windows Server versions, or another type of Linux. Besides the operating system XEN also converts the physical hardware devices into a set of virtual resources dedicated for the deployed virtual machines used by end users on a particular machine.
XEN is a so-called micro-kernel hypervisor that implements the seperation between policy and the mechanism itself. In other words it implements all required virtualization mechanisms but the policy how the virtualization should be performed by a dedicated domain installation. A guest operating system can then use hypervisor mechanisms to have access to the underlying physical devices. This means it provides no device drivers natively that in turn enables the XEN hypervisor to stay relativily small compared to other software in this area. Other virtualization software tools are KVM, VMWare ESX Server or VMWare Workstation. They all slightly vary with respect to the supported host operating systems and their virtualization architecture.
More about the XEN hypervisor
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