lec04-Xen - VMM a Brief History Virtual Machine Monitor: a

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1 VMM – a Brief History Virtual Machine Monitor: a software-abstraction layer that partitions the HW into one or more virtual machines 1960s: used for multiplexing the scarce general purpose computing platforms among multiple applications 1980s: multitasking OSes + low HW costs Rendered VMMs obsolete Consequently, no hardware support for virtualization in the CPU architectures of the time (e.g., x86)
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And now… 2 Compared to “ cloud computing ” (in red)
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3 Why this revival? Virtual Machine Monitor: a software-abstraction layer that partition the HW into one or more virtual machines 1960s: used for multiplexing the scarce general purpose computing platforms among multiple applications 1980s: multitasking OSes + low cost hardware Rendered VMMs obsolete 2000s: multitasking OSes + low cost hardware Revived VMMs
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4 Cause and Solution Increased OS functionality : More capable OSes: Fragile and vulnerable Low cost hardware : Proliferation of machines: Underused With high space and management overhead Solution: back to one application per machine Per virtual machine This time: VMM as a means of multiplexing hardware for server consolidation Solution for security and reliability
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5 VMM: Decoupling the HW and the OS by a layer of indirection Uniform view of underlying HW, so virtual machines can run on any hardware Complete encapsulation of a virtual machine’s software state, so migration is much easier Total mediation of all interactions between the virtual machine and the underlying HW, thus allowing strong isolation between VMs
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6 Big Picture (and Terminology) Guest OS Virtual Machine
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7 Xen (Original slides by Kishore Ramachandran adapted by Anda Iamnitchi)
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8 Key points Goal : extensibility and flexibility akin with Exokernel/Micro-kernel goals Main difference : granularity of operating systems rather than applications running several commodity operating systems on the same hardware simultaneously without sacrificing performance or functionality Why? Application mobility Server consolidation Co-located hosting facilities Distributed web services Secure computing platforms
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9 Possible Virtualization Approaches Standard OS (such as Linux, Windows) Meta services (such as grid) for users to install files and run processes Administration, accountability, and performance isolation become hard Retrofit performance isolation into OSs Accounting resource usage correctly can be an issue unless done at the lowest level and very fine granularity (e.g., Exokernel) Xen approach Multiplex physical resource at OS granularity
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This note was uploaded on 02/17/2012 for the course COP 6611 taught by Professor Staff during the Spring '08 term at University of South Florida - Tampa.

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lec04-Xen - VMM a Brief History Virtual Machine Monitor: a

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