31 Questions
What is the primary characteristic of a distributed system according to the text?
A collection of autonomous computing elements
What is the implication of each node having its own notion of time in a distributed system?
It leads to fundamental synchronization and coordination problems
How do nodes in a distributed system typically communicate with each other?
By communicating only with their known neighbors
What is the relationship between the nodes in a distributed system?
The nodes are interdependent and must collaborate to appear as a single system
What is the purpose of the 'overlay network' mentioned in the text?
To manage the dynamic set of neighbors that each node can communicate with
What is the key challenge mentioned in the text regarding the collection of autonomous nodes in a distributed system?
Managing group membership and node authorization
What is the main problem with applying replication according to the text?
Inconsistencies due to modifying one copy
Why does always keeping copies consistent require global synchronization?
To ensure data integrity
What does global synchronization on each modification preclude according to the text?
Large-scale solutions
How can the need for global synchronization be reduced?
By tolerating inconsistencies
What is highlighted as being application dependent in the text?
Tolerating inconsistencies
Why does having multiple copies lead to inconsistencies?
"Always keeping copies consistent"
What is the key characteristic of a distributed system that emphasizes the system operating the same way regardless of user interaction?
Distribution transparency
Which of the following is NOT a well-known example of an overlay network?
Cloud computing platforms
What is the primary role of middleware in distributed systems?
To provide a common interface for applications across different computers
Which of the following is a key challenge in hiding partial failures in a distributed system?
The inevitability of some nodes failing at any given time
Which of the following is NOT a characteristic of a structured overlay network?
Nodes have references to randomly selected other nodes
What is the primary design goal of middleware in distributed systems?
To provide a common set of components and functions for applications
Which of the following is NOT considered a component of scalability in distributed systems?
Processing power of individual nodes
What is the main challenge that modern distributed systems still face today, according to the text?
Geographical and administrative scalability
What is the typical solution used to address size scalability in distributed systems?
Deploying multiple powerful servers operating independently in parallel
Which of the following is NOT a key component of scalability in distributed systems?
Reliability of individual nodes
Why do many developers of modern distributed systems use the term scalable without clearly explaining why their system actually scales?
They have only accounted for size scalability, not geographical or administrative scalability
What is one of the canonical examples of supporting resource sharing mentioned?
Peer-to-peer assisted multimedia streaming
What does 'The network is the computer' refer to?
A concept by John Gage about cloud computing
What is a type of distribution transparency discussed in the text?
Replication
Why is full distribution transparency considered challenging according to the text?
Due to the practical impossibility of hiding network failures
What is one of the disadvantages of full distribution transparency mentioned in the text?
Higher performance costs
When dealing with users in different time zones, what aspect may favor exposing distribution according to the text?
Easing user understanding
What cannot be hidden when aiming for full distribution transparency according to the text?
Communication latencies
Why is distinguishing a slow computer from a failing one considered challenging according to the text?
'Slow' computers often mimic failure symptoms
Study Notes
Introduction to Distributed Systems
- A distributed system is a collection of autonomous computing elements that appears to its users as a single coherent system.
- Characteristics of distributed systems include:
- Autonomous computing elements (nodes) that can operate independently
- Single coherent system: users perceive a single system despite multiple nodes
Autonomous Computing Elements
- Each node has its own notion of time, leading to synchronization and coordination problems
- Nodes may have different notions of group membership and authorized communication
Overlay Networks
- Organization of nodes in a distributed system: each node communicates with its neighbors
- Overlay networks support:
- Resource sharing
- Distribution transparency
- Openness
- Scalability
Types of Overlay Networks
- Structured overlay networks: each node has a well-defined set of neighbors (e.g., tree, ring)
- Unstructured overlay networks: each node has references to randomly selected other nodes
Middleware and Distributed Systems
- Middleware: the operating system of distributed systems, providing a common interface for applications
- Components of middleware include:
- Commonly used functions and components that do not need to be implemented by applications separately
Design Goals for Distributed Systems
- Scalability is a key goal, with dimensions including:
- Size scalability (number of users and processes)
- Geographical scalability (maximum distance between nodes)
- Administrative scalability (number of administrative domains)
Scalability Techniques
- Replication is a technique for scaling, but it can lead to inconsistencies and require global synchronization
- Tolerating inconsistencies may reduce the need for global synchronization, but this is application-dependent
Distribution Transparency
- Distribution transparency aims to hide the differences between accessing local and remote resources
- Types of transparency include:
- Access transparency
- Location transparency
- Relocation transparency
- Migration transparency
- Replication transparency
- Concurrency transparency
- Failure transparency
Degree of Transparency
- Aiming for full distribution transparency may be too much, as it can:
- Hide communication latencies
- Hide failures of networks and nodes
- Make it difficult to distinguish between slow computers and failing ones
- Make it difficult to ensure that a server performed an operation before a crash
- Cost performance and expose the distribution of the system
- Require significant resources to maintain replicas and perform write operations
Exposing Distribution
- Exposing distribution may be beneficial in certain cases, such as:
- Location-based services
- Dealing with users in different time zones
- Making it easier for users to understand what's happening in the system
Test your knowledge on the introduction to distributed systems based on selected slides from the 3rd edition of the book 'Distributed Systems' by M. van Steen and A. S. Tanenbaum. Explore the definition and characteristic features of distributed systems.
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