XEN Basic

Xen Virtualization Introduction

Virtualization is one of most important technique in nowaday computer system.With virtualization mechanism , services such as cloud computing, application mobility and co-location facility can be implement.

Xen is the virtual machine monitor that first proposed in SOSP'03 by University of Cambridge. Xen is aim to provide high performance resource management. In the other hand , Xen hypervisor must isolate each virtual machine from others.Finally Xen must support wide range of  heterogeneity operating system.

http://www.cl.cam.ac.uk/research/srg/netos/papers/2003-xensosp.pdf

Virtualization type

In 2003 , Xen was first proposed with paravirtualization architecture. Just after Intel proposed VT-x in 2005 , Xen release version 3.04 which support hvm client.  Figure 1 show both two type's architecture. 

Figure 1 : Xen Architecture

Paravirtualization 

Compare to full virtualization used by VMware's ESX server which not need to modify guest OSes, Xen employ paravirtualization that need to make some minor change to guest OSes. After modification, Xen can offer the same abstraction between virtual machine and underlying hardware ,so that performance can be improved.   

Hardware-assisted Virtualization

After VT-x published, consistent view between sensitive instruction and privilege instruction let full virtualization easily.That is , all the sensitive instruction execute in guest will cause a trap to VMM. With the power of VT-x, Xen are modify to support HVM which has no need to modify guest OSes.  Latter in 2006, "Extending Xen with Intel Virtualization Technology" was published in Intel Technology Journal .This article states changes for Xen to support HVM.

Xen Basic installation

Reference

1. “Extending Xen* with Intel® Virtualization Technology,” Intel Technology Journal vol. 10, no. 03. 2006.
2. P. Barham, B. Dragovic, K. Fraser, S. Hand, T. Harris, A. Ho, R. Neugebauer, I. Pratt, and A. Warfield, “Xen and the Art of Virtualization Categories and Subject Descriptors,” SOSP'03.
3. Xen official website, http://www.xen.org/download/index_3.4.4.html
4. WikiPedia ,  http://en.wikipedia.org/wiki/Xen