NTRODUCTIONTO DISTRIBUTED SYSTEMS DISTRIBUTED COORDINATION ...
EEDC - Distributed Systems
-
Upload
maria-stylianou -
Category
Technology
-
view
624 -
download
1
description
Transcript of EEDC - Distributed Systems
Execution Environments for Distributed Computing
Distributed Systems
EEDC34330
Master in Computer Architecture, Networks and Systems - CANS
Homework number: 1Group number: EEDC-7
Group members:
Georgia Christodoulidou – [email protected]
Ioanna Tsalouchidou – [email protected]
Maria Stylianou – [email protected]
2
Contents
• Definitions• Need for DS• Characteristics• Trade-offs• Examples• Differentiation with parallel systems• Challenges
3
What is a Distributed System (DS)?
• No single definition for distributed systems
• Two representative definitions:• “A system in which hardware and software components located
at network computers communicate and coordinate their actions only by message passing.” ~ Coulouris
• “A distributed system is a collection of independent components that appear to the users of the system as a single computer.” ~ Tanenbaum
4
What is a Distributed System (DS)?
5
Why do we need DS?
• Workload distribution among the nodes
Performance improved
• Information distribution and sharing
• Resource sharing
Reliability
Data Preservation &
Replication
6
Characteristics of DS
• Concurrent execution• Message passing communication• Resource sharing• No global clock• Lack of knowledge of the global state of the DS by
any single process
7
Trade-offs
• Communication via insecure network
• Topology is not stable => Latency increases
• Message loss
• Bandwidth is limited
• Multiple administrators => Difficult to manage the system
8
Examples of DS
• World Wide Web - www• Distributed File Systems - DFS• Database Systems• Distributed Operating Systems
9
Differentiation with Parallel Systems
• No need of shared memory Communication via message passing
• No need of homogeneity DS consists of different types of hardware and software.
10
Challenges
• Heterogeneity• Distribution transparency• Fault tolerance• Scalability• Concurrency• Openness• Security
11
Challenges - Heterogeneity
• Inter-operation of the heterogeneous components• Differences between components in
• Operating systems• Hardware and Communication architectures• Programming languages• Software
12
Challenges - Distribution Transparency
• The perception of the system as a whole and not as a collection of independent components
13
Challenges - Fault Tolerance, Scalability
Fault Tolerance• Multiple failures
• Hardware• Software• Network
• Maintain availability despite failures!
Scalability• The system should
remain effective, even with a significant increase • in the number or
resources• in the number of users
14
Challenges - Concurrency, Openness
Concurrency• Manage concurrent
access to shared resources• Scheduling• Dependencies• Deadlocks
Openness• Possibility of new
resource-sharing services to be added
• Available to be used by users
15
Challenges - Security
• Resources should be used the way they are supposed to
• Only authorized users should access the resources• Confidentiality• Integrity• Availability• Non-repudiation
16
Thank you!
Questions?