Dave Elliman Xen and virtualization
Virtual Machines <ul><li>A  virtualization  layer is interposed between the hardware and the operating system s </li></ul>...
The idea has caught on <ul><li>An old idea in fact IBM 370 in 1972! Xen is far more flexible </li></ul><ul><li>Sun’s Virtu...
Used in web servers <ul><li>You want to host a web site? You are likely to purchase a virtual server </li></ul><ul><li>It ...
Security can be Enhanced <ul><li>Potentially huge security benefits </li></ul><ul><li>Provides isolation between operating...
Why only use 1 machine? <ul><li>Hypervisors can cooperate across a cluster or farm of servers </li></ul><ul><li>Hypervisor...
Scalability and Robustness <ul><li>One can load balance the machines </li></ul><ul><li>One can add more machines to the cl...
More of Xen <ul><li>Developed by Ian Pratt at Cambridge </li></ul><ul><li>Bought by Citrix Systems in 2007 </li></ul><ul><...
Porting an OS to Xen <ul><li>Requires less than 2% of the total lines of code to be modified. </li></ul>04/04/10 Xen and V...
Performance <ul><li>Some overhead – 2% to 5% depending on memory and other resources </li></ul><ul><li>Xen seems to have a...
Enterprise Computing? <ul><li>Highly relevant! Offers: </li></ul><ul><ul><li>Scalability </li></ul></ul><ul><ul><li>Reliab...
References <ul><li>University of Cambridge Xen page </li></ul><ul><ul><li>http://www.cl.cam.ac.uk/Research/SRG/netos/xen/ ...
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Xen

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Xen

  1. 1. Dave Elliman Xen and virtualization
  2. 2. Virtual Machines <ul><li>A virtualization layer is interposed between the hardware and the operating system s </li></ul><ul><li>Multiple operating systems can run on the same hardware simultaneously </li></ul><ul><li>They can be the same o/s or different </li></ul><ul><li>Each is isolated from the others and unaware of their existence </li></ul><ul><li>A Virtual Machine Monitor is needed to accomplish this: The VMM or Hypervisor </li></ul><ul><li>The overhead must be reasonably small – this has driven changes to chip design to support virtualization </li></ul><ul><ul><li>(   Intel VT  (codenamed Vanderpool) and  AMD 's is referred to as  AMD-V  (codenamed Pacifica) </li></ul></ul>04/04/10 Xen and Virtualization
  3. 3. The idea has caught on <ul><li>An old idea in fact IBM 370 in 1972! Xen is far more flexible </li></ul><ul><li>Sun’s VirtualBox </li></ul><ul><li>Vmware ESX Server </li></ul><ul><li>Microsoft just released Hyper-V </li></ul><ul><li>Xen is the most widely used by far – available as open source but now owned by Citrix Inc. </li></ul><ul><li>Developed at Cambridge University </li></ul>04/04/10 Xen and virtualization
  4. 4. Used in web servers <ul><li>You want to host a web site? You are likely to purchase a virtual server </li></ul><ul><li>It looks like it is your machine but really it is a virtual machine running under Xen </li></ul><ul><li>As a hosting company you can buy 50 or 100 times less hardware! </li></ul><ul><li>Not surprising this caught on </li></ul>04/04/10 Xen and virtualization
  5. 5. Security can be Enhanced <ul><li>Potentially huge security benefits </li></ul><ul><li>Provides isolation between operating system instances and multiplexes physical resources across the running virtual machines. </li></ul><ul><li>Security holes in the operating system can be caught in the hypervisor which has a simpler and leaner API. </li></ul><ul><li>It is easier to code a secure hypervisor than a secure O/S </li></ul><ul><li>Of course a vulnerability in the hypervisor could be a HUGE risk, spreading infection rapidly. </li></ul>04/04/10 Xen and Virtualization
  6. 6. Why only use 1 machine? <ul><li>Hypervisors can cooperate across a cluster or farm of servers </li></ul><ul><li>Hypervisors can move a virtual environment from machine to machine </li></ul><ul><li>This can be done in say 200mS – the user does not notice a delay! </li></ul><ul><li>Why is this a brilliant idea? </li></ul>04/04/10 Xen and virtualization
  7. 7. Scalability and Robustness <ul><li>One can load balance the machines </li></ul><ul><li>One can add more machines to the cluster easily offering more performance </li></ul><ul><li>Trees of clusters are possible for really high performance </li></ul><ul><li>A busy machine can offload some processes to a less busy one </li></ul><ul><li>An unreliable machine or one suffering power failure can migrate its processes </li></ul>04/04/10 Xen and virtualization
  8. 8. More of Xen <ul><li>Developed by Ian Pratt at Cambridge </li></ul><ul><li>Bought by Citrix Systems in 2007 </li></ul><ul><li>Hosts operating systems such as Linux and Windows. </li></ul><ul><ul><li>Some source code modifications are necessary especially for Windows </li></ul></ul><ul><li>Is completely software based and requires no special hardware support. </li></ul><ul><ul><li>Full virtualization, in which the virtual hardware is identical to the underlying physical hardware, is virtually impossible on the x86 architecture. New chips will solve this. </li></ul></ul><ul><ul><li>Xen provides a similar, but not quite identical view of the hardware. </li></ul></ul><ul><li>Support unmodified application binaries. </li></ul><ul><li>Support fully functional, multi-application operating systems a guests. </li></ul>04/04/10 Xen and Virtualization
  9. 9. Porting an OS to Xen <ul><li>Requires less than 2% of the total lines of code to be modified. </li></ul>04/04/10 Xen and Virtualization The User Software runs on the Guest OS without requiring modification.
  10. 10. Performance <ul><li>Some overhead – 2% to 5% depending on memory and other resources </li></ul><ul><li>Xen seems to have a lower overhead than its competitors </li></ul>04/04/10 Xen and the Art of Virtualization Diana Carroll
  11. 11. Enterprise Computing? <ul><li>Highly relevant! Offers: </li></ul><ul><ul><li>Scalability </li></ul></ul><ul><ul><li>Reliability </li></ul></ul><ul><ul><li>Robustness </li></ul></ul><ul><ul><li>Security </li></ul></ul><ul><li>An arguably tidier solution than large enterprise application containers or special cluster operating systems </li></ul><ul><li>Xen + Spring + Hibernate and WCF with WPF Client looks pretty good to me. </li></ul>04/04/10 Xen and virtualization
  12. 12. References <ul><li>University of Cambridge Xen page </li></ul><ul><ul><li>http://www.cl.cam.ac.uk/Research/SRG/netos/xen/ </li></ul></ul><ul><li>Wikipedia entry for Xen </li></ul><ul><ul><li>http://en.wikipedia.org/wiki/Xen </li></ul></ul>04/04/10 Xen and Virtualization

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