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CS550: Distributed OS Lecture 1 Page 1X.Sun (IIT)
CS550• Distributed Operating Systems (Advanced Operating
• Like a uniprocessor operating system • Manage multiple CPUs transparently to the
user• Each processor has its own hardware cache
– Maintain consistency of cached data• Shared variable versus message passing
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Multicomputer Operating Systems
1.14
• More complex than multiprocessor OS– Because communication has to be through explicit message
passing
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Network Operating System
1-19
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Network Operating System• Employs a client-server model
– Minimal OS kernel– Additional functionality as user processes
1-20
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• Users are aware of multiplicity of machines. Access to resources of various machines is done explicitly by– Remote logging into the appropriate remote
machine.– Transferring data from remote machines to local
machines, via the File Transfer Protocol (FTP) mechanism.
Network-Operating Systems
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Distributed Operating System
• Users not aware of multiplicity of machines.• Manages resources in a distributed system
– Seamlessly and transparently to the user• Looks to the user like a centralized OS
– But operates on multiple independent CPUs• Provides transparency
– Location, migration, concurrency, replication,…• Presents users with a virtual uniprocessor
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Middleware-based Systems• General structure of a distributed system as
middleware.
1-22
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What is Middleware
Software above the operating system but below the application programMiddleware refers to the software that is common to multiple applications and builds on the network transport services to enable ready development of new applications and network servicesCORBA, DCOM, Java RMI, Grid
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Middleware Layer
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Technical Challenges
• The changing environment– Computing world has changed and middleware has to
adapt to this ever changing environment• Architecture
– New technological advances impose changes in established middleware architecture
• Dynamic configuration– Dynamic changes in system configuration will be
inherent characteristics of future computing environments.
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Any Questions?
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Questions?
•What is the difference between operating system and (software) system?•What is the difference between network OS and Distributed OS?•What is the difference between Distributed OS and Distributed (software) system?•What is middleware?•What is the difference between middleware and Distributed (software) system?
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Structure of OSsFive major intellectual achievements
• Processes• Memory management• Information protection and security• Scheduling and resource management• System structure
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Process A process is an active entity and is realized by data structure• Process space: each process is assigned a
virtual address space– Text region, the code being executed by the
process– Data region, holding global variables– Stack region, holding execution context of the
program• Threat
– User-level threat, system-level threat
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Memory Management• Main-memory management• Second-storage management• I/O system • Virtual Memory: allows program to address
memory without regard to the amount of mainmemory physically available