What is server virtualization

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Server virtualization is a process of splitting server resources into smaller parts. On typical server there is one operating system running, having all server resources for itself. In case there is no load on a server, all those resources are wasted.

In virtualized server, there is more than one operating system working, each sharing slice of central processing unit’s (CPU) power. These systems are called virtual servers. Since virtual servers share same CPU, you get much better utilization of server resources.

Different server virtualization technologies use different ways to isolate one virtual operating system from another. At the moment these are the main technologies:

  • Xen
  • KVM
  • OpenVZ
  • Hyper-V
  • VMware

Choosing a XEN provider

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When looking for quality XEN hosting provider, consider these points:

  • Hardware that hosting company is running. CPUs must be Intel Xeons;
  • Can you start small?
  • Is there place for growth?
  • Time in business.
  • Can they offer extra support?

XEN Virtualization types

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XEN operates in two ways:

XEN Paravirtualization (PV)

When XEN is working in PV mode, guest operating systems “know” that they are running as virtual machines. This means that guest operating system must be changed. For example by making updates to Linux kernel. Unfortunately, this means that not all operating systems can be used in PV mode. For example Windows(R) can not be run in PV mode. Overhead is small when XEN is working in PV mode and so performance in virtual server is near native.

XEN Hardware assisted virtualization (HVM)

When XEN is working in HVM mode, guest operating system is not aware that it is running as a guest. This means that all required devices for OS to run are emulated by XEN. No changes are required to guest operating system to run in HVM mode. On the other hand Virtualization must be supported in host node hardware. This is done by virtualization features in modern processors and other peripherals like network cards.

What is XEN?

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Xen (XEN) is one of several server virtualization technologies. It used to divide one physical server into several smaller servers. XEN also isolates one virtual server from another. Each virtual server looks like a normal physical server. This allows to:

  • Consolidate several servers into one
  • Increase server utilization
  • Provide rapid provisioning
  • Increase fault tolerance
  • Secure OS separation
  • the ability to support legacy software as well as new OS instances on the same computer

XEN opperates in one of two ways:

  • PV – paravirtualization
  • HVM – hardware assisted virtualization

XEN is free technology. You can install it yourself or you can rent a XEN virtual server.