Allows operating systems to run applications within other OSes Vast and growing

Allows operating systems to run applications within

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Allows operating systems to run applications within other OSes Vast and growing industry Emulation used when source CPU type different from target type (i.e. PowerPC to Intel x86) Generally slowest method When computer language not compiled to native code – Interpretation Virtualization – OS natively compiled for CPU, running guest OSes also natively compiled Consider VMware running WinXP guests, each running applications, all on native WinXP host OS VMM (virtual machine Manager) provides virtualization services
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1.52 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9 th Edition Computing Environments - Virtualization Use cases involve laptops and desktops running multiple OSes for exploration or compatibility Apple laptop running Mac OS X host, Windows as a guest Developing apps for multiple OSes without having multiple systems QA testing applications without having multiple systems Executing and managing compute environments within data centers VMM can run natively, in which case they are also the host There is no general purpose host then (VMware ESX and Citrix XenServer)
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1.53 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9 th Edition Computing Environments - Virtualization
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1.54 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9 th Edition Computing Environments – Cloud Computing Delivers computing, storage, even apps as a service across a network Logical extension of virtualization because it uses virtualization as the base for it functionality. Amazon EC2 has thousands of servers, millions of virtual machines, petabytes of storage available across the Internet, pay based on usage Many types Public cloud – available via Internet to anyone willing to pay Private cloud – run by a company for the company’s own use Hybrid cloud – includes both public and private cloud components Software as a Service ( SaaS ) – one or more applications available via the Internet (i.e., word processor) Platform as a Service ( PaaS ) – software stack ready for application use via the Internet (i.e., a database server) Infrastructure as a Service ( IaaS ) – servers or storage available over Internet (i.e., storage available for backup use)
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1.55 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9 th Edition Computing Environments – Cloud Computing Cloud computing environments composed of traditional OSes, plus VMMs, plus cloud management tools Internet connectivity requires security like firewalls Load balancers spread traffic across multiple applications
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1.56 Silberschatz, Galvin and Gagne ©2013 Operating System Concepts – 9 th Edition Computing Environments – Real-Time Embedded Systems Real-time embedded systems most prevalent form of computers Vary considerable, special purpose, limited purpose OS, real-time OS Use expanding Many other special computing environments as well