1. An Introduction to Xen Prof. Chih-Hung Wu
Dept. of Electrical Engineering
National University of Kaohsiung
URL:

2. History of virtualization development
1965 IBM M44/44X paging system
1965 IBM System/ virtual memory hardware
1967 IBM CP-40 (January) and CP-67 (April) time-sharing
1972 IBM VM/370 run VM under VM
1997 Connectix First version of Virtual PC
1998 VMWare U.S. Patent 6,397,242
1999 VMware Virtual Platform for the Intel IA-32 architecture
2000 IBM z/VM
2001 Connectix Virtual PC for Windows
2003 Microsoft acquired Connectix
2003 EMC acquired Vmware
2003 VERITAS acquired Ejascent
2005 HP Integrity Virtual Machines
2005 Intel VT
2006 AMD VT
2005 XEN
2006 VMWare Server
2006 Virtual PC 2006
2006 HP IVM Version 2.0
2006 Virtual Iron 3.1
2007 InnoTek VirtualBox
2007 KVM in Linux Kernel
2007 XEN in Linux Kernel

3. What Is Xen?
Xen aims to be able to execute multiple operating systems on one physical x86 machine:
Support popular OS (Linux, Windows XP, NetBSD),
Scalable up to around 100 VMs,
Securely,
With close-to-native performance.
Xen is a virtual machine monitor (VMM).

4. What is Xen?
The Xen® hypervisor, the powerful open source industry standard for virtualization, offers a powerful, efficient, and secure feature set for virtualization of x86, x86_64, IA64, PowerPC, and other CPU architectures. It supports a wide range of guest operating systems including Windows®, Linux®, Solaris®, and various versions of the BSD operating systems.
Xen.org releases Xen The Yankee Groups Third Annual Virtualization Survey reports a significant increase of commercial Xen-based solutions which represent 17 percent of total market share.
"I think Xen is a great product. It is easy to use. But most importantly is the very active community around it...", Werner Vogels,CTO Amazon.com from his video interview on Virtualization.com

5. Xen Architecture
Linux: 1.36% XP: 0.04%
Source: Xen and the Art of Virtualization (Xen 1.x.) Published at SOSP 2003

6. Xen Jargon The hypervisor Guest Operating System Domain
The Xen VMM
A particular Xen version which handles low level functionality
Guest Operating System
The operating system that Xen hosts
Domain
The virtual machine under which a guest operating system executes
Guest OS and a domain similar to idea of a program and a process
Linux: 1.36% XP: 0.04%

7. Xen Architecture (Cont.)
Domain0 can use the admin interface to command the hypervisor,
Domain0 uses a privileged kernel (Dom0 kernel) capable of accessing the hardware of the machine,
Other guests use a DomU kernel which is typically more restricted.
Linux: 1.36% XP: 0.04%

8. Xen 3.4.0 Available from Xen Source (http://www.xen.org )
In association with University of Cambridge (
Support for 64-Bit and 32-way machines
Supports IntelVT and AMD-V
Linux support only, Windows expected later this year
Open Source Product – One of the most actively maintained projects in the open source community
$ - Free
Latest Current Version: Xen 3.4.0

9. Xen
Xen already is bundled in some distributions, CentOS 5.3, Fedora Core 4, Debian and SuSE Professional 9.3
The Fedora Project has RPMs for installing Xen, and other Linux distros have prepared installation packages for Xen as well.

10. Types of virtualization
Two categories exist
Full Virtualization
Paravirtualization

11. Paravirtualization -- Xen Approach
Virtual machine is NOT 100% functionally equivalent to the hardware
Xen uses paravirtualization instead
Paravirtualization is a process where the guest operating system is modified to run in parallel with other modified systems
Advantage: Improved performance
Disadvantage: The hosted operating system must be modified before it can be hosted by the Xen Hypervisor (can be difficult)

12. Hypervisor Control In Xen In VMWare
Domain0 is given greater access to the hardware and the hypervisor. It has:
A guest OS running above the domain
Hypervisor Manager software to manage elements within other existing domains.
In VMWare
Host OS acts underneath the domain.

13. HVM in Xen Paravirtualization HVM for full virtualization
Xen patches the kernel.
HVM for full virtualization
Xen supports full virtualization so that the kernel can run on it unpatched.
For example, both Intel VT and AMD Pacifica processors will include such support.

14. Virtual Networking in Xen
Source:

15. Virtual Networking in Xen
Source:

16. Virtual Networking in Xen
Source:

17. Virtual Networking in Xen
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18. Virtual Networking in Xen
Source:

19. Live Migration Xen supports live migration over LAN,
Uses ‘pre-copy’ method:
Iteratively copy memory,
Pause the VM,
Copy rest of the memory,
Start VM in on new machine.
ARP is used to signal the network that the IP has moved.
Disk is provided by NAS.

20. Requirements For Running Xen
A working Linux distribution using the GRUB bootloader and running on a P6-class (or newer) CPU,
More than 1GB RAM (suggested)
iproute2, bridge-utils, gcc, binutils, make, libcurl-devel, zlib-dev, python-dev,
Don’t need to reinstall to try it:
Build Xen in your existing Linux install (which will become Domain0),
Use a file backed filesytem for guests.
You can try it using a bootable live CD.

21. Current Status (Xen 3.x) Secure isolation between VMs,
Resource control and QoS,
Only guest kernel needs to be ported,
All user-level apps and libraries run unmodified
Linux 2.4/2.6, NetBSD, CentOS 5, FreeBSD, Plan9, and more
Execution performance is close to native,
Supports the same hardware as Linux x86,
Live Relocation of VMs between Xen nodes.
Source : Overview of Xen 3.0. Describes the progression from Xen 2.0 to 3.0.

22. Performance
Relative performance on native Linux (L), Xen/Linux (X), VMware Workstation 3.2 (V), and User Mode Linux (U).