Overview of System Virtualization
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Transcript of Overview of System Virtualization
SYSTEM VIRTUALIZATIONAndre Odendaal
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Section Agenda
• Definition
• Real Benefits
• History
• Hypervisor Architecture
• Hardware Virtualization Assistance
• Considerations
• Conclusion
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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
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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– SaaS (Software as a Service)– IaaS (Infrasture as a Service)
From VMWare Virtualization Overview © 2006
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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
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Hypervisor Technology
• A popular method of virtualization is paravirtualizationusing 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 paravirtualizedand are validated and executed by the hypervisor on either the hardware or the host OS
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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
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
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Hardware Virtualization Assistance
• The Popek and Goldberg Formal Requirements for Virtualizable Third Generation Architectures are a set of requirements for sufficient hardware virtualization– Equivalence – A program
running under VMM should exhibit the same behaviour if run on the machine directly
– Resource Control – The VMM should be in complete control of the virtualized resources
– Efficiency – Major of machine instructions should be allowed to execute with VMM intervention
• Initially the x86 architecture was unsuitable for virtualization– Ring compression (unable to
change privilege level in 64-bit mode)
– Ring aliasing (system calls reveal privilege level)
– Address Space Compression (VMM address space isn’t protected)
– Non-Privileged Sensitive Instructions (some system calls are not privileged)
– Silent Privilege Failures (some system calls fail without trapping)
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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)
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Conclusion
• Virtualization is a broad IT initiative
• Requires management to be successful
• Long history at all sectors of IT (Hardware, Operating System, Virtual Machines)
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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
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Questions
Thank you
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