D Distributed Operating Systems Dionicio D. Gante, Genevev G. Reyes & Vanylive T. Galima
Distributed System is used to describe a system with the following characteristics: • Consists of several computers that do not share a memory or a clock; • The computers communicate with each other by exchanging messages over a communication network; and • Each computer has its own memory and runs its own operating system.
Definition of Distributed OS It extends the concepts of resource management and user friendly interface for shared memory computers a step further, encompassing a distributed computing system consisting of several autonomous computers connected by a communicating network.
Issues in Distributed OS • Global Knowledge • Naming • Scalability • Compatibility • Process Synchronization • Resource Management • Security • Structuring
What are the Advantages of Distributed Systems Over Traditional Time-Sharing Systems?
The Main Advantage of Distributed Systems is: • They have a decisive price/ performance advantage over more traditional time-sharing systems
Other Significant Advantages: • Resource Sharing • Enhanced Performance • Improved Reliability and availability • Modular expandability
Tanenbaum and Renesse classified distributed systems into three broad categories, namely: the minicomputer model, the workstation model and the processor pool model.
Categories of Distributed Systems • Minicomputer Model • Workstation Model • Processor Pool Model
Mutual exclusion is a collection of techniques for sharing resources so that different uses do not conflict and cause unwanted interactions.
What are the differences between mutual exclusion in a single computer systems from distributed systems?
To maintain mutual exclusion; that is, to guarantee that only one request accesses the critical section at a time.
Characteristics are considered important in a mutual exclusion algorithm: • Freedom from Deadlocks • Freedom from Starvation • Fairness • Fault Tolerance
How to measure the performance • The number of messages necessary per CS invocation. • The synchronization delay • The response time