Distributed Systems Quiz

Questions and Answers

Which of the following distributed systems is NOT mentioned?

Google's BigTable

Amazon's Dynamo

Hadoop

Apache's Kafka (correct)

Independent things fail independently is a principle of distributed systems.

True

What is one consequence of distribution in distributed programming?

Information travels at the speed of light.

The CALM theorem is associated with ______ consistency models.

eventual Signup and view all the answers

Match the following terms with their descriptions:

Distance = Impacts communication speed in distributed systems Time = Influences the design of distributed algorithms Consistency models = Determines how distributed components sync data Independent failures = Suggests that system components can fail without impacting each other Signup and view all the answers

Which of the following is a focus of the text?

Providing an accessible introduction to key concepts Signup and view all the answers

The text elaborates on the idea that distance and time interact in distributed systems.

True Signup and view all the answers

Name one of the algorithms mentioned that will be covered in the content.

CRDTs Signup and view all the answers

What is scalability primarily concerned with?

Ability to handle growing workloads Signup and view all the answers

A scalable system will have increased administrative costs as more nodes are added.

False Signup and view all the answers

What are the three aspects of growth that are particularly interesting to look at in scalable systems?

Size scalability, Geographic scalability, Administrative scalability Signup and view all the answers

Latency refers to the state of being __________; delay, a period between the initiation of something and the occurrence.

latent Signup and view all the answers

Match the following definitions with their corresponding terms:

Performance = The amount of useful work done compared to time and resources used Latency = The state of being latent; delay Throughput = Rate of processing work Response Time = Time taken to respond to a request Signup and view all the answers

Which of the following is NOT a characteristic of performance?

High administrative costs Signup and view all the answers

Geographic scalability allows the use of multiple data centers to improve response times.

True Signup and view all the answers

Why is low latency considered an interesting aspect of performance?

Because it has a strong connection with physical limitations. Signup and view all the answers

The key challenge in a distributed system is the overhead from __________ and coordination.

computers Signup and view all the answers

What is primarily meant by 'size scalability'?

The addition of more nodes making the system faster without increasing latency Signup and view all the answers

Which of the following is NOT a high-level goal of distributed systems?

Portability Signup and view all the answers

The CAP theorem states that it is impossible for a distributed data store to simultaneously provide all three guarantees: Consistency, Availability, and Partition tolerance.

True Signup and view all the answers

What two basic tasks must any computer system accomplish?

storage and computation Signup and view all the answers

The two basic methods of replication discussed include __________ and Paxos.

2PC Signup and view all the answers

Match the terms with their definitions:

CAP theorem = States limitations in achieving consistency, availability, and partition tolerance Vector clocks = Used for tracking the causal relationships in distributed systems 2PC = A least fault-tolerant replication method Dynamo = A system designed with weak consistency guarantees Signup and view all the answers

What is a common challenge faced in distributed systems that can affect performance?

Network communication between nodes Signup and view all the answers

Weak consistency guarantees are always preferable to strong consistency in all distributed systems.

False Signup and view all the answers

What is the primary advantage of high-end hardware in the context of distributed systems?

Replacing slow network accesses with internal memory accesses Signup and view all the answers

Adding a new machine ideally __________ the performance and capacity of a distributed system.

increases Signup and view all the answers

Which consistency model is associated with CRDTs and the CALM theorem?

Eventual Consistency Signup and view all the answers

What does fault tolerance in a system refer to?

The ability of a system to behave in a predefined manner when faults occur Signup and view all the answers

An anomaly is considered the same as an error in system behavior.

False Signup and view all the answers

What are the two physical factors that constrain distributed systems?

The number of nodes and the distance between nodes. Signup and view all the answers

The minimum latency for communication between distant nodes increases with _____ distance.

geographic Signup and view all the answers

Match the types of models with their descriptions:

System model = Defines the timing of operations Failure model = Describes how systems cope with failures Consistency model = Specifies data consistency guarantees Abstraction = Simplifies complex systems by removing irrelevant details Signup and view all the answers

Which of the following best describes an effective abstraction in a distributed system?

It simplifies manageable aspects while focusing on the problem at hand Signup and view all the answers

Increasing the number of nodes in a distributed system generally improves availability.

False Signup and view all the answers

What is a primary criterion implied in the discussion of system design that relates to user comprehension?

Intelligibility Signup and view all the answers

A system that makes _____ guarantees may allow for greater performance but can be harder to reason about.

weaker Signup and view all the answers

What generally happens when geographic distance increases in a distributed system?

Minimum latency for communication increases Signup and view all the answers

What does 'latency' refer to in the context described?

The time between when something happens and when it is visible. Signup and view all the answers

A system with no changes should have a latency problem.

False Signup and view all the answers

What is the formula for availability?

Availability = uptime / (uptime + downtime) Signup and view all the answers

In a distributed system, latency is not impacted by the amount of old data but by the speed at which new data becomes __________.

visible Signup and view all the answers

Match the following availability percentages with their allowed downtime per year:

90% = More than a month 99% = Less than 4 days 99.9% = Less than 9 hours 99.999% = Less than an hour Signup and view all the answers

What primarily affects the availability of a system?

The number of redundant components. Signup and view all the answers

Fault tolerance in a distributed system ensures that it can remain operational even when some components fail.

True Signup and view all the answers

What is the minimum latency in a distributed system primarily limited by?

The speed of light and hardware latency. Signup and view all the answers

Availability is assessed as a percentage, such as __________ for three nines.

99.9% Signup and view all the answers

Which of the following allows a distributed system to tolerate failures?

Redundancy among components. Signup and view all the answers

What assumption is made about messages in distributed algorithms when considering network reliability?

Messages are never lost or delayed. Signup and view all the answers

A network partition occurs when nodes stop operating while the network remains functional.

False Signup and view all the answers

What is the term for when messages may be lost or delayed due to network issues?

Network partition Signup and view all the answers

In distributed systems, _________ messages can be lost.

sent Signup and view all the answers

Match the following types of node failures with their descriptions:

Crashed nodes = Nodes that are no longer operational Partitioned nodes = Nodes that are operational but unable to communicate Faulty nodes = Nodes that can still process but may produce incorrect output Operational nodes = Nodes that function normally Signup and view all the answers

What is the primary benefit of strong consistency in replication models?

Simplicity in programming as if data is not replicated Signup and view all the answers

Weaker consistency models can provide lower latency and higher availability.

True Signup and view all the answers

What does the term 'abstraction' refer to in distributed systems?

Abstraction simplifies complex realities, allowing for easier management and understanding of systems. Signup and view all the answers

The tension between multiple nodes and the desire for a system to work like a __________ is a key consideration in distributed programming.

single system Signup and view all the answers

Match the following consistency models with their characteristics:

Strong consistency = Allows programming as if data is not replicated Weaker consistency = Provides lower latency and higher availability Consistency model = A framework to manage data synchronization in replication Abstraction = Simplifies complex realities for better understanding Signup and view all the answers

Which of the following reflects the essence of abstraction according to the content?

Abstractions ignore some elements to manage complexity. Signup and view all the answers

What does the CAP theorem address?

The CAP theorem outlines the trade-offs between Consistency, Availability, and Partition tolerance in distributed systems. Signup and view all the answers

Why are impossibility results important in distributed systems?

They simplify problems, showing limitations within defined constraints. Signup and view all the answers

Every situation in distributed systems is unique, making abstraction unnecessary.

False Signup and view all the answers

The simplicity of a consistency model is crucial because it provides clean semantics for __________.

programmers Signup and view all the answers

Which of the following best describes the environment in a distributed system?

No shared memory or shared clock Signup and view all the answers

Nodes in a distributed system can fail and recover independently.

True Signup and view all the answers

What type of failure model do most distributed systems assume?

Crash-recovery failure model Signup and view all the answers

A robust system model makes ___ assumptions about its environment.

weak Signup and view all the answers

Match the following properties of nodes with their descriptions:

Ability to execute a program = Hosts for computation Ability to store data = Volatile and stable storage A clock = May not be accurate Deterministic algorithms = Local state determines messaging Signup and view all the answers

Which of the following is a characteristic of communication links in a distributed system?

Connects individual nodes allowing message exchange Signup and view all the answers

Byzantine fault tolerance is commonly handled in real-world commercial systems.

False Signup and view all the answers

What is one consequence of having local knowledge in distributed systems?

Global state may be out of date Signup and view all the answers

Communication links in a distributed system allow messages to be sent in ___ direction(s).

either Signup and view all the answers

What characteristic is NOT associated with nodes in a distributed system?

Global shared state Signup and view all the answers

What are the two basic techniques to handle data sets in distributed systems?

Partitioning and Replication Signup and view all the answers

Partitioning allows partitions to fail independently, increasing the overall system availability.

True Signup and view all the answers

What is the main purpose of data replication in distributed systems?

To improve performance and availability. Signup and view all the answers

The _____ theorem addresses the challenges of achieving both availability and consistency in distributed systems.

CAP Signup and view all the answers

Match the following techniques with their main benefits:

Partitioning = Limits data examination and improves availability Replication = Increases computing power and fault tolerance Either technique = Reduces latency Neither technique = Creates a single point of failure Signup and view all the answers

What is a common challenge faced when partitioning data?

Inefficient access across partitions Signup and view all the answers

Replication reduces latency but can complicate the consistency of the dataset.

True Signup and view all the answers

What should a system designer assess when picking between replication and partitioning?

Design objectives and specific implementation needs. Signup and view all the answers

The technique of _____ allows for parallel processing by dividing the dataset into smaller independent sets.

partitioning Signup and view all the answers

Which of the following best describes replication?

Creating copies of data on multiple machines Signup and view all the answers

Study Notes

Introduction to Distributed Systems

Recent distributed systems include Amazon's Dynamo, Google's BigTable, and Apache's Hadoop.
Main ideas are accessibility, key concepts for further reading, and understanding core constraints of distributed programming.
Two crucial aspects: information travels at light speed and independent failures occur independently.
Focus on interaction between distance, time, and consistency models in commercial data centers.
Key protocols and new methods like CRDTs and the CALM theorem are introduced.

Basics of Distributed Systems

Distributed programming solves problems using multiple computers instead of a single machine.
Central tasks: storage and computation, often due to size and cost constraints.
Commodity hardware offers the best value at scale, emphasizing fault-tolerant software.
Performance improvements are limited by communication bottlenecks between nodes.
Scalability principles define how performance and capacity must improve with added nodes.

Key Concepts of Scalability

Scalability is the ability to manage growing workloads without performance degradation.
Size scalability: More nodes should enhance performance linearly.
Geographic scalability: Multiple data centers reduce response times and manage latency.
Administrative scalability: Adding nodes shouldn't increase administrative overhead.
Performance metrics include response time, throughput, and resource utilization, each with its own tradeoffs.

Performance and Latency

Performance measures the useful work relative to time and resources used.
Latency refers to the delay between an action and its observable effect, linked to physical travel times and hardware limits.
Minimum latency cannot be avoided, constrained by speed of light and hardware operations.
High latency in distributed systems can arise from operational distance and requires careful management.

Availability and Fault Tolerance

System availability reflects the proportion of time a system functions correctly.
Fault tolerance is the system's capacity to handle failures gracefully without complete breakdown.
Redundancy is key for high availability across various components (nodes, servers, data centers).
Availability metrics are quantified (e.g., 99.999% equates to about 5 minutes of downtime annually).

Constraints in Distributed Systems

Two major physical limitations: node count and inter-node distance, impacting performance and administrative costs.
More independent nodes raise failure probabilities, reducing overall system reliability.
Distance contributes to communication latency, necessitating careful system design to mitigate downsides.

Abstractions and Models

Abstractions simplify complex systems by identifying relevant facets pertinent to solving specific problems.
Different models, such as system models (synchronous/asynchronous) and consistency models (strong/eventual), provide clarity.
Effective abstractions enhance operability but must balance performance with comprehensibility.

Data Distribution Techniques

Key methods for organizing data are partitioning and replication.
Partitioning divides datasets for parallel processing, enhancing performance and resilience to independent failures.
Replication copies data to multiple nodes, improving availability and reducing latency for client interactions.
Choosing between methods is dependent on application needs and performance criteria.

Summary of Design Techniques

Smart system design leverages partitioning to manage data growth while ensuring operational efficiency and independent node reliability.
Understanding and applying distributed algorithms critically shapes successful implementation, aligning with specific system goals.### Partitioning and Replication
Partitioning involves dividing data into segments optimized for expected access patterns.
Independent partitions can lead to inefficiencies, such as cross-partition access and uneven growth rates.
Replication creates copies of data across multiple servers, enhancing computation and reducing latency.

Advantages of Replication

Increases performance by providing additional computing power and bandwidth through data copies.
Enhances availability by having multiple copies of data, requiring more failures before downtime occurs.
Supports scaling and fault tolerance in systems.
Addresses slow computation and I/O by replicating data to reduce latency and improve throughput.

Consistency Models

The consistency model determines how replicated data remains synchronized across nodes.
Strong consistency allows programming as if data isn't replicated, ensuring reliability.
Weaker consistency models can reduce latency and enhance availability but may complicate programming semantics.

Levels of Abstraction

Distributed programming involves managing multiple nodes while striving for a unified system experience.
Abstractions simplify complex systems but inevitably exclude unique aspects of each scenario.
Proper abstractions allow for manageable problem statements while retaining essential characteristics.

System Models in Distributed Systems

Distributed systems operate with no shared memory or synchronized clocks; nodes execute concurrently and independently.
Nodes possess local knowledge only, leading to potential delays or inaccuracies in global state representation.
Failures can occur independently, complicating system behavior.

Assumptions and Properties

System models specify assumptions regarding nodes, communication links, and timing.
Robust models are based on minimal assumptions, increasing algorithmic tolerance to diverse environments.
Nodes are designed to execute programs, with capabilities for volatile and stable data storage.

Communication and Network Links

Links connect nodes and facilitate message passing, often with assumptions of FIFO ordering and possible message loss.
A network partition can disrupt communication without node failures, causing messages to be lost or delayed.
Understanding failure models is crucial; most systems use a crash-recovery model, while Byzantine fault tolerance addresses arbitrary faults but is rarely practical.

Impossibility Results

Impossibility results clarify limitations within distributed systems based on specific assumptions or constraints.
They highlight essential characteristics that must be preserved in system design for optimal performance and reliability.

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Description

Test your knowledge on distributed systems concepts, including principles like independent failures and consistency models such as the CALM theorem. This quiz covers various key aspects of distributed programming and matching relevant terms to their definitions.