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
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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
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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
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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)
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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)
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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)
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