Distributed Systems (3rd Edition) - Chapter 01: Introduction (Selected Slides)
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What is the primary characteristic of a distributed system according to the text?

  • A collection of centralized computing elements
  • A collection of nodes with a static set of neighbors
  • A single coherent system with a global clock
  • A collection of autonomous computing elements (correct)

What is the implication of each node having its own notion of time in a distributed system?

  • It requires a global clock to be implemented across the system
  • It leads to fundamental synchronization and coordination problems (correct)
  • It leads to improved synchronization and coordination between nodes
  • It is not a problem as long as the nodes communicate regularly

How do nodes in a distributed system typically communicate with each other?

  • Through a central server that manages all communications
  • By broadcasting messages to all other nodes in the system
  • By using a fully connected topology where each node can talk to any other node
  • By communicating only with their known neighbors (correct)

What is the relationship between the nodes in a distributed system?

<p>The nodes are interdependent and must collaborate to appear as a single system (C)</p> Signup and view all the answers

What is the purpose of the 'overlay network' mentioned in the text?

<p>To manage the dynamic set of neighbors that each node can communicate with (C)</p> Signup and view all the answers

What is the key challenge mentioned in the text regarding the collection of autonomous nodes in a distributed system?

<p>Managing group membership and node authorization (B)</p> Signup and view all the answers

What is the main problem with applying replication according to the text?

<p>Inconsistencies due to modifying one copy (A)</p> Signup and view all the answers

Why does always keeping copies consistent require global synchronization?

<p>To ensure data integrity (D)</p> Signup and view all the answers

What does global synchronization on each modification preclude according to the text?

<p>Large-scale solutions (B)</p> Signup and view all the answers

How can the need for global synchronization be reduced?

<p>By tolerating inconsistencies (D)</p> Signup and view all the answers

What is highlighted as being application dependent in the text?

<p>Tolerating inconsistencies (C)</p> Signup and view all the answers

Why does having multiple copies lead to inconsistencies?

<p>&quot;Always keeping copies consistent&quot; (C)</p> Signup and view all the answers

What is the key characteristic of a distributed system that emphasizes the system operating the same way regardless of user interaction?

<p>Distribution transparency (A)</p> Signup and view all the answers

Which of the following is NOT a well-known example of an overlay network?

<p>Cloud computing platforms (C)</p> Signup and view all the answers

What is the primary role of middleware in distributed systems?

<p>To provide a common interface for applications across different computers (B)</p> Signup and view all the answers

Which of the following is a key challenge in hiding partial failures in a distributed system?

<p>The inevitability of some nodes failing at any given time (B)</p> Signup and view all the answers

Which of the following is NOT a characteristic of a structured overlay network?

<p>Nodes have references to randomly selected other nodes (C)</p> Signup and view all the answers

What is the primary design goal of middleware in distributed systems?

<p>To provide a common set of components and functions for applications (A)</p> Signup and view all the answers

Which of the following is NOT considered a component of scalability in distributed systems?

<p>Processing power of individual nodes (B)</p> Signup and view all the answers

What is the main challenge that modern distributed systems still face today, according to the text?

<p>Geographical and administrative scalability (A)</p> Signup and view all the answers

What is the typical solution used to address size scalability in distributed systems?

<p>Deploying multiple powerful servers operating independently in parallel (D)</p> Signup and view all the answers

Which of the following is NOT a key component of scalability in distributed systems?

<p>Reliability of individual nodes (B)</p> Signup and view all the answers

Why do many developers of modern distributed systems use the term scalable without clearly explaining why their system actually scales?

<p>They have only accounted for size scalability, not geographical or administrative scalability (D)</p> Signup and view all the answers

What is one of the canonical examples of supporting resource sharing mentioned?

<p>Peer-to-peer assisted multimedia streaming (A)</p> Signup and view all the answers

What does 'The network is the computer' refer to?

<p>A concept by John Gage about cloud computing (B)</p> Signup and view all the answers

What is a type of distribution transparency discussed in the text?

<p>Replication (C)</p> Signup and view all the answers

Why is full distribution transparency considered challenging according to the text?

<p>Due to the practical impossibility of hiding network failures (C)</p> Signup and view all the answers

What is one of the disadvantages of full distribution transparency mentioned in the text?

<p>Higher performance costs (C)</p> Signup and view all the answers

When dealing with users in different time zones, what aspect may favor exposing distribution according to the text?

<p>Easing user understanding (D)</p> Signup and view all the answers

What cannot be hidden when aiming for full distribution transparency according to the text?

<p>Communication latencies (D)</p> Signup and view all the answers

Why is distinguishing a slow computer from a failing one considered challenging according to the text?

<p>'Slow' computers often mimic failure symptoms (D)</p> Signup and view all the answers

Flashcards

Distributed System

A collection of independent computers that work together to appear as a single system to users.

Autonomous Computing Element

Individual computer in a distributed system that can operate independently.

Synchronization Problem

Difficulties coordinating actions across multiple computers with different internal times.

Overlay Network

A network built on top of another network, organizing nodes in a distributed system.

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Structured Overlay

An overlay network with nodes having defined relationships (like a tree or ring).

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Unstructured Overlay

Overlay network with nodes connected to randomly chosen other nodes.

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Resource Sharing

Ability of nodes in a distributed system to access and use each other's resources.

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Middleware

Software that acts as an interface between applications and the distributed system.

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Scalability (Size)

The ability of a distributed system to handle increasing numbers of users and processes.

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Scalability (Geographical)

System's ability to support increasing distance between nodes.

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Scalability (Administrative)

Ability to add more administrative domains without impacting the system.

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Replication

Creating multiple copies of data or resources across different computers.

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Inconsistencies

Differences in data values across replicated copies.

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Access Transparency

Hiding whether a resource is local or remote.

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Location Transparency

Hiding the physical location of resources.

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Relocation Transparency

Hiding the movement of resources.

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Migration Transparency

Concealing movement of resources from users.

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Replication Transparency

Hiding the replication of resources.

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Concurrency Transparency

Hiding how multiple users access resources.

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Failure Transparency

Concealing failures of resources, networks, or nodes.

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Distribution Transparency

Making access to resources as easy as local resource access.

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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

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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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