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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