Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
CHAPTER 1: INTRODUCTION CHAPTER OUTLINE System Definitions Hardware Concepts Software Concepts Client/Server Model System Definitions Traditional Uniprocessor Operating Systems Resource Manager (system’s view) – processor, information, memory, device Extended Machine (user’s view) – virtual concepts With goals: efficiency, flexibility, robustness Recent Technological Advances Widespread low-cost high-performance PCs High-speed network interconnection Emerging Applications Concurrent/parallel Distributed Collaborative Distributed Systems to Support New Applications (user’s view) – Transparency: a single computer view of multiple computer systems (system’s view) – Distributions: decentralized/autonomous, cooperative/collaborative Unique Problems (Limitations) in Distributed Systems lack of global state information lack of global clock (or time) failures of system components (processors, communication networks) Transparency - access, location, migration, relocation, replication, concurrency, failure, persistence Interoperability – interface, standard, openness, separation of model/policy/mechanism Middleware – organization for implementation of distributed systems Models – file, communication (RPC), object Layers – system, application Underlying Operating Systems for Distributed Systems Distributed Operating Systems – transparency for multiprocessor and homogeneous multiple computer systems Network Operating Systems – interoperability/portability/openness for heterogeneous systems and networks Additional goals: Scalability – size, geographical distance, administrative complexity – asynchronous communication, distribution, caching Robustness – security, reliability, privacy – cryptographic schemes, fault-tolerance, dispersion Hardware Concepts Shared Memory Multiprocessor Systems Bus – tightly coupled Switched – cross-point, interconnection network (e.g., Omega network), etc. Homogeneous Multiple Computer Systems Bus – tightly/loosely coupled (through message passing) Switched – grid, cube, interconnection network – routing Emulating Shared-Memory in Message-Passing Systems (DSM) Migration Replication Thrashing and false sharing Message Passing Heterogeneous Multiple Computer Systems Networks Software Concepts Major Issues in Uniprocessor OS Virtual machine Multi-level protection (mode) Minimum kernel (microkernel) Additional Issues in Multiprocessor DOS Multiprocessor scheduling Synchronization – semaphore, monitor, and etc. Additional Issues in Multiple Computer DOS Communication primitives – send/receive – naming, buffering and blocking Distributed synchronization Relationship between synchronization and communication Major Issues in Network OS (NOS) Network protocols for interoperability Network services – remote access and resource sharing – telnet, ftp, smtp, http, nfs More Issues for Distributed Processing in Network Environment Remote execution and process migration Load sharing and balancing Collaborative/cooperative application MIDDLEWARE-BASED DISTRIBUTED SYSTEMS Middleware: scalability and openness of NOS and transparency of DOS Services: locating services, group management, authentication/authorization, etc. Communication: reliable multicast, atomic transaction, etc. Middleware Models NFS RPC Distributed Objects Distributed Documents Client/Server Model Interaction > communication > access resource > request/reply Dumb/thin/heavy weight client Vertical distribution: user interface/application server/database server Horizontal distribution: parallelizing servers Parallelizing clients: P2P Some Emerging Computing Paradigms Ubiquitous/pervasive computing Mobile agent-based computing Mobile/wireless computing Grid computing P2P computing