30-06-2012, 05:44 PM
Distributed Systems Major Design Issues
[attachment=26378]
Definition:
Distributed operating system:
Integration of system services presenting a transparent view of a multiple computer system with distributed resources and control.
Consisting of concurrent processes accessing distributed shared or replicated resources through message passing in a network environment.
Problems Unique to Distributed Systems
Distributed Operating Systems: [3]
Generation: Third Generation Operating System.
Characteristics: Global view of file system, name space, time, security, computational power.
Goal: Single computer view of multiple computer system (transparency)
Distributed Operating System Goals:
Efficiency
Consistency
Robustness
Identification / Name
Design Issue Example: Resource identification [2]
The resources in a distributed system are spread across different computers and a naming scheme has to be devised so that users can discover and refer to the resources that they need.
An example of such a naming scheme is the URL (Uniform Resource Locator) that is used to identify WWW pages. If a meaningful and universally understood identification scheme is not used then many of these resources will be inaccessible to system users.
Synchronization Types
Barrier Synchronization:
Process must reach a common synchronization point before they can continue:
Condition Coordination:
A process must wait for a condition that will be set asynchronously by other interacting processes to maintain some ordering of execution.
Mutual Exclusion:
Concurrent processes must have mutual exclusion when accessing a critical shared resource.
Synchronization Issues:
State information sent by messages:
Typically only partial state information is known about other processes making synchronization difficult.
Information not current due to transfer time delay.
Decision if process may continue must rely on a message resolution protocol.
Centralized Coordinator:
Central point of failure
Deadlocks
Circular Waiting for the other process
Deadlock detection and recovery strategies.
[attachment=26378]
Definition:
Distributed operating system:
Integration of system services presenting a transparent view of a multiple computer system with distributed resources and control.
Consisting of concurrent processes accessing distributed shared or replicated resources through message passing in a network environment.
Problems Unique to Distributed Systems
Distributed Operating Systems: [3]
Generation: Third Generation Operating System.
Characteristics: Global view of file system, name space, time, security, computational power.
Goal: Single computer view of multiple computer system (transparency)
Distributed Operating System Goals:
Efficiency
Consistency
Robustness
Identification / Name
Design Issue Example: Resource identification [2]
The resources in a distributed system are spread across different computers and a naming scheme has to be devised so that users can discover and refer to the resources that they need.
An example of such a naming scheme is the URL (Uniform Resource Locator) that is used to identify WWW pages. If a meaningful and universally understood identification scheme is not used then many of these resources will be inaccessible to system users.
Synchronization Types
Barrier Synchronization:
Process must reach a common synchronization point before they can continue:
Condition Coordination:
A process must wait for a condition that will be set asynchronously by other interacting processes to maintain some ordering of execution.
Mutual Exclusion:
Concurrent processes must have mutual exclusion when accessing a critical shared resource.
Synchronization Issues:
State information sent by messages:
Typically only partial state information is known about other processes making synchronization difficult.
Information not current due to transfer time delay.
Decision if process may continue must rely on a message resolution protocol.
Centralized Coordinator:
Central point of failure
Deadlocks
Circular Waiting for the other process
Deadlock detection and recovery strategies.