Lecture 1: Introduction

Question 1

Distributed Systems

Answer 1

A set of cooperating computers communicating over a network to achieve a coherent task. Examples include storage for big websites, big data computations like MapReduce, and peer-to-peer file sharing.

Question 2

Decentralization

Answer 2

The absence of a central server in a system, where each node acts as both a client and a server. This can lead to increased robustness and fault tolerance.

Question 3

Fault Tolerance

Answer 3

The ability of a system to continue operating properly in the event of failure of one or more components.

Question 4

Registers

Answer 4

The fastest form of storage directly built into the CPU. Registers store small amounts of data and instructions being processed by the CPU, enabling nearly instantaneous access.

Question 5

Nonvolatile Memory

Answer 5

Storage medium that retains data even when power is turned off, such as NAND flash memory used in SSDs and USB drives. Offers faster read and write speeds compared to traditional magnetic and optical storage.

Question 6

Symmetric Multiprocessing (SMP)

Answer 6

Multiprocessor system architecture where all processors are treated equally and share access to all system resources, including memory and I/O devices.

Question 7

Asymmetric Multiprocessing (AMP)

Answer 7

Multiprocessor system architecture where one processor is designated as the master and controls the system, while the other processors act as subordinate processors and perform specialized tasks.

Question 8

Observer Pattern

Answer 8

Design pattern where an object, known as the subject, maintains a list of its dependents, called observers, and notifies them of any state changes, enabling them to react accordingly.

Question 9

Name two common approaches to achieving fault tolerance in distributed systems.

Answer 9

Two common approaches are availability, where the system continues to operate despite certain failures, and recoverability, where the system can recover from failures and resume normal operation after repairs.

Question 10

What are some tools used for achieving fault tolerance in distributed systems?

Answer 10

Non-volatile storage, such as hard drives or flash drives, is commonly used to store checkpoints or logs of system state to recover from failures.

Question 11

How does scalability relate to fault tolerance in distributed systems?

Answer 11

Scalability allows distributed systems to handle failures by adding more resources or nodes to compensate for failures, maintaining performance despite disruptions.

Question 12

What is fault tolerance, and why is it important in distributed systems?

Answer 12

Fault tolerance is the ability of a system to continue operating properly in the event of failure of one or more components. It’s crucial in distributed systems due to the inherent complexity and potential for failures in large-scale deployments.

Question 13

What are some implementation topics commonly encountered in distributed systems?

Answer 13

Common implementation topics include remote procedure call (RPC), threads, and concurrency control mechanisms like locks.

Question 14

What are the main infrastructure components in distributed systems?

Answer 14

The main infrastructure components are storage, communication, and computation.

Question 15

What are some examples of distributed systems applications?

Answer 15

Examples include storage for big websites, big data computations such as MapReduce, and peer-to-peer file sharing.

Question 16

What is the core concept of distributed systems?

Answer 16

The core concept of distributed systems is a set of cooperating computers communicating over a network to achieve a coherent task.

Question 17

What are some reasons for building distributed systems?

Answer 17

Reasons include achieving high performance through parallelism, fault tolerance, handling naturally distributed problems, and achieving security through isolation.

Question 18

Describe the scalability challenge in distributed systems.

Answer 18

Scalability refers to the ability to handle increasing workload or data by adding resources. The challenge lies in ensuring that adding resources results in proportional performance improvements.

Question 19

How do partial failures differ from complete failures in distributed systems?

Answer 19

Partial failures occur when some components of the system stop working while others continue, whereas complete failures involve the entire system becoming inoperative.

Question 20

What is the role of threads in distributed systems?

Answer 20

Threads are used for concurrent programming in distributed systems to harness multi-core CPUs and structure concurrent operations to simplify programming.

Question 21

Explain the concept of recoverability in fault tolerance.

Answer 21

Recoverability refers to the system’s ability to resume normal operation after a failure, typically by saving state information and restoring it when the failure is resolved.

Question 22

What is the significance of non-volatile storage in fault tolerance?

Answer 22

Non-volatile storage allows systems to store critical state information persistently, enabling them to recover from failures by restoring the system’s previous state.

Question 23

How do distributed systems address the challenge of network failures?

Answer 23

Distributed systems often incorporate redundancy and error-handling mechanisms to mitigate the impact of network failures, such as replicating data or employing routing protocols.

Question 24

What are the primary goals of building abstractions in distributed systems?

Answer 24

The goals are to simplify the interface for applications, hide the distributed nature of the underlying infrastructure, and enable easier development of distributed applications.

Question 25

How do distributed systems handle the challenge of concurrency?

Answer 25

Concurrency in distributed systems is managed using techniques like thread synchronization, locks, and distributed algorithms to ensure consistency and prevent race conditions.

Question 26

What is a common scalability issue when dealing with web servers and databases?

Answer 26

The bottleneck often shifts from web servers to databases as the number of web servers increases, requiring careful design to maintain performance.

Question 27

What is the significance of non-volatile storage in fault tolerance?

Answer 27

Non-volatile storage allows systems to recover from failures by storing checkpoints or logs of system states.

Question 28

What is the primary challenge in managing replicated copies for fault tolerance?

Answer 28

The challenge is ensuring that replicas stay in sync and do not drift apart.

Question 29

What is consistency in the context of distributed systems?

Answer 29

Consistency refers to ensuring that all nodes in a distributed system have the same view of the data at any given time.

Question 30

Why is consistency challenging in distributed systems with replication?

Answer 30

Replication introduces the risk of inconsistency due to delays in updating replicas and the possibility of concurrent updates.