Overview of System Virtualization


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Overview of System Virtualization

  1. 1. Andre OdendaalSYSTEM VIRTUALIZATION 1
  2. 2. Section Agenda• Definition• Real Benefits• History• Hypervisor Architecture• Hardware Virtualization Assistance• Considerations• Conclusion 2
  3. 3. Definition• Definition: Abstraction of the hardware resources into multiple execution environments• Comes from need to make more effective use of hardware• Approaches – Full - Hardware is completely emulated by the virtual machine – Paravirtualization - The virtual machine provides an API and the guest OS is modified to run on the virtual machine From Silberschatz, Galvin & Gagne Operating System Concepts © 2005 3
  4. 4. Real Benefits• Not just for – Development & Testing – Consolidating physical servers• It’s a change in IT infrastructure – Creates hardware independence and mobility – Isolation from conflicts and service availability – Manage downtime and disaster recovery• Creating new opportunities From VMWare Virtualization Overview © 2006 – SaaS (Software as a Service) – IaaS (Infrasture as a Service) 4
  5. 5. History• 1964 - IBM developed Control Program-40 (CP-40) which emulated the System/360 architecture for multiple users.• 1972 – IBM released VM/370 for the System/370 which included virtual machine support, real device support and greater hardware exploitation. IBM also developed versions of MVS, UNIX, DOS/VSE and PC/DOS to run under VM• 1970’s – Virtualization is eclipsed by microcomputers• 1981 – IBM announced Extended Architecture (XA) which, among other things, had specialized I/O processors that were part of the hardware• 1999 - VMWare Workstation is released• 2001 - VMware ESX Server is released• 2003 - The first public release of Xen was made available• 2007 - Sun announced the Sun xVM• 2008 – Sun acquired VirtualBox 5
  6. 6. Hypervisor Technology• A popular method of virtualization is paravirtualization using a hypervisor to manage the guest OS also called Virtual Machine Monitor (VMM)• The term hypervisor comes from the hyper call made by the guest OS to the virtual machine which is similar to a supervisor call made by an operating system to the Kernel• The hypervisor manages the operation levels of the guest OS by creating a virtual kernel mode and virtual user mode. Privileged instructions are paravirtualized and are validated and executed by the hypervisor on either the hardware or the host OS 6
  7. 7. Hypervisor Technology• Hosted – Hypervisor installed on host OS and manages guest OS – Provides the broadest range of hardware configurations• Hypervisor (Bare-metal) – First layer on top of the hardware – Provides greater scalability, robustness and performance From VMWare Virtualization Overview © 2006 7
  8. 8. Hardware Virtualization Assistance• Hardware can also be optimized for virtualization. Example include: – Virtual Memory – Memory Management Units – IO Virtualization• Hardware supporting virtualization – IBM – System/370 – Intel – x86 Intel VT – AMD – x86 AMD V – Sun – UltraSPARC 8
  9. 9. Hardware Virtualization Assistance• The Popek and Goldberg • Initially the x86 architecture Formal Requirements for was unsuitable for Virtualizable Third Generation virtualization Architectures are a set of – Ring compression (unable to requirements for sufficient change privilege level in 64-bit hardware virtualization mode) – Equivalence – A program – Ring aliasing (system calls running under VMM should reveal privilege level) exhibit the same behaviour if – Address Space Compression run on the machine directly (VMM address space isn’t – Resource Control – The VMM protected) should be in complete control – Non-Privileged Sensitive of the virtualized resources Instructions (some system calls – Efficiency – Major of machine are not privileged) instructions should be allowed – Silent Privilege Failures (some to execute with VMM system calls fail without intervention trapping) 9
  10. 10. Considerations• Management Complexity – Be prepared and have a plan – Make use of ITIL (Information Technology Infrastructure Library) for years of best practice• Pitfalls – Hardware Failure • All your eggs in one basket – Over commitment • Over or under use of resources – Operational Processors • VM sprawl vs. Server sprawl – Skills shortage • Virtualization requires specific skills (Configuration, Tuning & Troubleshooting) 10
  11. 11. Conclusion• Virtualization is a broad IT initiative• Requires management to be successful• Long history at all sectors of IT (Hardware, Operating System, Virtual Machines) 11
  12. 12. References• Bob DuCharme The Operating Systems Handbook © 2001• Silberschatz, Galvin & Gagne Operating System Concepts © 2005• VMWare Virtualization Overview © 2006• IBM Introduction to the New Mainframe: z/VM Basics © 2007• IBM IBM Systems Virtualization © 2005• Barham, Dragovic, Fraser, Hand, Harris, Ho, Neugebauery, Pratt, Wa rfield Xen and the Art of Virtualization © 2003• Fisher-Ogden Hardware Support for Efficient Virtualization• Business Trends Quarterly Virtualization: Big Picture Q1 2007• Business Trends Quarterly The Pros and Cons of Virtualization Q1 2007 12
  13. 13. Questions Thank you 13