Hadoop and MapReduce Concepts Quiz
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Questions and Answers

What is the least preferred scenario for executing a mapper in Hadoop?

  • Executing the mapper on the nodes in different racks (correct)
  • Executing the mapper on the same node
  • Executing the mapper on a different node in the same rack
  • Executing the mapper on multiple nodes within the same rack
  • Which industry uses Hadoop for predictive maintenance by leveraging IoT device data?

  • Energy (correct)
  • Telecommunications
  • Financial services
  • Retail
  • How do telecommunications companies utilize Hadoop-powered analytics?

  • To optimize supply chain management
  • To create trading algorithms for financial services
  • To execute predictive maintenance on their infrastructure (correct)
  • To enhance traditional retail analytics
  • What is one application of big data analytics in the public sector?

    <p>Anticipating and preventing disease outbreaks (C)</p> Signup and view all the answers

    Which of the following best describes how retailers use Hadoop?

    <p>To analyze structured and unstructured data for customer insights (C)</p> Signup and view all the answers

    What are the two main components of a MapReduce job?

    <p>Map task and Reduce task (D)</p> Signup and view all the answers

    In the context of MapReduce, what does the 'splitting' mode do?

    <p>Divides a file into key-value pairs of data (C)</p> Signup and view all the answers

    What is the purpose of the map task in a MapReduce job?

    <p>To associate each key with a count of values (B)</p> Signup and view all the answers

    What occurs after the mapping phase in a MapReduce process?

    <p>Shuffling (B)</p> Signup and view all the answers

    What does the reducer do with the values it receives?

    <p>Calculates the sum of all numbers for each key (D)</p> Signup and view all the answers

    What best describes task parallelism?

    <p>Dividing a task into sub-tasks processed on separate nodes (A)</p> Signup and view all the answers

    How does data parallelism differ from task parallelism?

    <p>It divides a dataset into multiple sub-datasets for processing (D)</p> Signup and view all the answers

    What happens with the output from the sub-tasks in parallel processing?

    <p>It is combined to obtain the final set of results (D)</p> Signup and view all the answers

    What is the primary purpose of data munging?

    <p>To transform raw data into valuable formats for analytics (B)</p> Signup and view all the answers

    Which type of data processing involves executing tasks on multiple separate machines?

    <p>Distributed data processing (B)</p> Signup and view all the answers

    What is a key characteristic of the MapReduce framework?

    <p>It divides a larger task into smaller concurrent sub-tasks (D)</p> Signup and view all the answers

    In data munging, what step comes after accessing the raw data?

    <p>Transforming the data using algorithms (D)</p> Signup and view all the answers

    Which of the following best describes centralized data processing?

    <p>All processing occurs on a single machine (C)</p> Signup and view all the answers

    What is a major benefit of using real-time data analysis with tools like Apache Spark?

    <p>It provides high scalability and fault tolerance (C)</p> Signup and view all the answers

    What does the term 'data locality' refer to in the context of data processing?

    <p>Focusing data processing near the data source to reduce latency (C)</p> Signup and view all the answers

    What is one of the steps involved in the data processing workload?

    <p>Measuring the amount and nature of data processed over time (A)</p> Signup and view all the answers

    What happens when the active NameNode fails in a Hadoop HA cluster?

    <p>A passive NameNode becomes active. (B)</p> Signup and view all the answers

    Which method does Hadoop HDFS use to ensure fault tolerance?

    <p>Replication of users' data on different machines. (C)</p> Signup and view all the answers

    What is the primary benefit of data locality in Hadoop?

    <p>Reduced network congestion. (A)</p> Signup and view all the answers

    What is a drawback of Hadoop related to data processing?

    <p>Cross-switch network traffic due to large data volume. (C)</p> Signup and view all the answers

    What technique is used to improve efficiency between a mapper and reducer in Hadoop?

    <p>Combiner. (D)</p> Signup and view all the answers

    In which scenario is intra-rack data locality most applicable?

    <p>When mapper execution on the same datanode is impossible. (D)</p> Signup and view all the answers

    What is a key factor in ensuring optimal performance in a Hadoop cluster?

    <p>Proper configuration and tuning of the cluster. (D)</p> Signup and view all the answers

    What does fault tolerance mainly refer to in Hadoop HDFS?

    <p>Functioning despite component failures. (C)</p> Signup and view all the answers

    What is a unique feature of Hadoop regarding cluster scaling?

    <p>Horizontal scaling can add nodes on the fly. (D)</p> Signup and view all the answers

    What problem does the high availability feature in Hadoop address?

    <p>Single point of failure in older versions. (A)</p> Signup and view all the answers

    In which way does Hadoop HDFS ensure data availability if a DataNode fails?

    <p>By redirecting users to another DataNode with the same data. (D)</p> Signup and view all the answers

    What is the primary role of the NameNode in HDFS?

    <p>To maintain the filesystem tree and metadata. (D)</p> Signup and view all the answers

    Which type of data processing does Spark primarily support?

    <p>Realtime processing with all input data available. (A)</p> Signup and view all the answers

    What is a common characteristic of in-memory processing?

    <p>It allows faster processing but not permanent storage. (D)</p> Signup and view all the answers

    What is one way that vertical scaling is typically implemented in a Hadoop cluster?

    <p>By adding more disks to the existing nodes. (A)</p> Signup and view all the answers

    What does the term 'scalability' refer to in the context of Hadoop?

    <p>The ability to expand or shrink the cluster as needed. (C)</p> Signup and view all the answers

    What characterizes batch workloads in terms of processing?

    <p>They typically involve large quantities of data with sequential read/writes. (B)</p> Signup and view all the answers

    Which of the following systems commonly processes workloads in batches?

    <p>Online Analytical Processing systems (D)</p> Signup and view all the answers

    What is a notable feature of transactional workloads compared to batch workloads?

    <p>They process data interactively with low latency. (D)</p> Signup and view all the answers

    What role do clusters play in processing large datasets?

    <p>They provide fault tolerance and redundancy in processing. (D)</p> Signup and view all the answers

    Which of the following best describes the data handling in transactional workloads?

    <p>It primarily involves random reads and writes. (C)</p> Signup and view all the answers

    What is the principle of divide-and-conquer in the context of data processing?

    <p>It allows for independent and parallel processing of smaller dataset parts. (C)</p> Signup and view all the answers

    What is the primary function of the MapReduce processing engine?

    <p>To execute a single run known as a MapReduce job. (D)</p> Signup and view all the answers

    Which of the following statements about operational systems is correct?

    <p>They are designed for online transactional processing. (B)</p> Signup and view all the answers

    Flashcards

    Data Munging

    The process of transforming and mapping data from one 'raw' data form into another format with the intent of making it more appropriate and valuable for various downstream purposes like analytics.

    Parallel Data Processing

    A task is divided into smaller sub-tasks that run concurrently, aiming to reduce execution time. This happens within a single machine with multiple processors.

    Distributed Data Processing

    Similar to parallel processing, but tasks are distributed across physically separate machines connected in a cluster, enabling processing large datasets.

    Processing Workload

    The amount and nature of data processed within a specific timeframe, defining the load and type of processing.

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    Data Processing

    Collecting, processing, manipulating, and managing data from various sources to generate meaningful information for the end user.

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    Centralized Data Processing

    Refers to a centralized approach to data processing where all operations occur within a single computer system.

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    Distributed Data Processing

    Involves distributing data processing across multiple machines, using a network to connect them. This allows for handling larger datasets and enhancing processing speed.

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    Batch Processing

    A processing approach where data is processed in batches and often involves delays. Think of it like a big batch of laundry - you wait for everything to be collected before you start washing.

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    Batch Workload

    A workload type characterized by large data volumes, sequential read/writes, and the execution of complex queries. It's like analyzing a whole company's sales history.

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    Transactional Processing

    A processing approach where data is processed interactively and without delay, leading to quick responses. Imagine buying a product online - you get instant feedback.

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    Transactional Workload

    A workload type involving small amounts of data, random reads and writes, and the execution of simple queries. Think of making a purchase online - small, individual actions.

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    Online Transaction Processing (OLTP)

    A type of system designed for transactional workloads. It's like an online store where each customer's purchase is processed immediately.

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    Online Analytical Processing (OLAP)

    A type of system designed for batch workloads. It's like analyzing a company's annual sales data to gain insights.

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    MapReduce

    A method for efficiently handling large datasets. It involves breaking down the data into smaller parts, Processing each part independently and then combining the results. Think of dividing a big puzzle into smaller pieces.

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    MapReduce Job

    A processing run within the MapReduce framework. Think of it as one complete cycle of dividing, processing, and combining data.

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    File Splitting in MapReduce

    The process of dividing a file into key-value pairs, where the key is the offset and the value is the line of data.

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    Mapping in MapReduce

    The logic that a programmer writes to process the value of each line, typically involving counting occurrences of specific items.

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    Shuffling in MapReduce

    The process of grouping values together based on their corresponding keys. This happens after the mapping phase and before the reduction phase.

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    Reduction in MapReduce

    The process of combining the values for each key, typically by summing them up. This happens after shuffling.

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    Task Parallelism

    A method of parallelization where a task is broken into smaller sub-tasks, and each sub-task is run on a separate processor, usually in a cluster. Sub-tasks usually execute different algorithms.

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    Data Parallelism

    A method of parallelization where a dataset is split into multiple smaller datasets, and each sub-dataset is processed in parallel, usually on different nodes in a cluster. All sub-datasets are processed using the same algorithm.

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    Distributed Computing

    A general approach to managing large datasets using a collection of computers working together. The data is distributed across nodes, and operations are performed in parallel on different parts of the data.

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    Real-time Processing

    A type of data processing that handles data as it arrives, allowing for immediate analysis and actions. For example, fraud detection systems.

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    In-memory Processing

    A data processing method where data is stored and manipulated in the computer's main memory, resulting in significantly faster processing. This is suitable for smaller datasets.

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    Scalability

    The ability to expand or shrink the size of a system (like a Hadoop cluster) based on workload demands.

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    Vertical Scaling

    Adding more resources to existing nodes in a cluster, for example, adding more disks to a Hadoop node.

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    Horizontal Scaling

    Adding more nodes to a cluster on the fly, without downtime, to increase the cluster's processing power. For example, adding more servers to a Hadoop cluster.

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    High Availability

    The ability of a system to remain functional even if one or more components fail, ensuring continuous operation and data availability. This is achieved in Hadoop HDFS through redundant data replication.

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    Single Point of Failure

    A single point of failure refers to a component in a system whose failure can lead to the entire system's failure. In Hadoop, the NameNode was a single point of failure in older versions.

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    Inter-Rack data locality

    When a Hadoop mapper is run on a node in a different rack than the data it needs to process due to resource constraints.

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    Least preferred scenario in Hadoop data locality

    A scenario in Hadoop where data is processed on a node in a different rack than the node where the data resides, leading to slower performance due to increased network latency.

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    Hadoop in financial services

    Financial institutions utilize Hadoop to analyze vast amounts of data to assess risk, create investment models, and develop complex trading algorithms.

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    Hadoop in retail

    Retailers leverage Hadoop to analyze various types of customer data to understand customer behavior, preferences, and trends to improve marketing and sales strategies.

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    Hadoop in the energy industry

    The energy industry uses Hadoop to analyze sensor data from Internet of Things (IoT) devices for predictive maintenance, optimizing equipment performance and reducing downtime.

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    What is the purpose of a NameNode in a Hadoop cluster, and how is high availability achieved?

    The NameNode is a critical component in a Hadoop cluster responsible for managing data blocks and metadata. To ensure high availability, Hadoop clusters run two NameNodes in an active/passive configuration, with one active and the other in standby. If the active NameNode fails, the standby node automatically takes over, ensuring uninterrupted file system operations.

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    What is fault tolerance in Hadoop, and how is it achieved?

    Fault tolerance in Hadoop refers to the system's ability to continue working even if some components fail. It's achieved through data replication, where data is copied onto multiple data nodes within the cluster. This redundancy ensures data availability even if a node goes down.

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    What is Data Locality in Hadoop, and what are its benefits?

    Data Locality in Hadoop is a technique that minimizes network traffic by bringing the processing power closer to the data. Instead of moving massive data to the processing nodes (like mappers and reducers), the data processing jobs are scheduled on the same nodes where the data resides.

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    What is Data Local Data Locality?

    Data Local Data Locality refers to the optimal scenario where the mapper processing the data is located on the same node as the data itself. This minimizes network overhead and maximizes the efficiency of data processing.

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    What is Intra-Rack Data Locality?

    Intra-Rack Data Locality occurs when the mapper processing the data is on a different node than the data but within the same physical rack. This is a less optimal scenario than Data Local, but it's still better than having the data and the mapper on different racks.

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    What is Inter-Rack Data Locality?

    Inter-Rack Data Locality is a data locality strategy in Hadoop where the mapper processing the data is located on a different node than the data and also on a different physical rack. This results in the highest network overhead and is generally least preferable.

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    Why is Data Locality important in Hadoop?

    Data Locality is crucial for efficient Hadoop operations. It minimizes network traffic, improves processing speeds, and maximizes cluster utilization by scheduling jobs on the nodes where the data is stored.

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    What are some best practices for optimizing Hadoop cluster performance?

    The Hadoop ecosystem provides various techniques to optimize cluster performance, including proper cluster configuration, effective data compression using LZO, and optimized data types for efficient storage and retrieval.

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    Study Notes

    DSC650: Data Technology and Future Emergence - Lecture 4: Data Munging

    • Lecture focuses on data munging, a crucial aspect of big data technology.
    • Data munging is the process of transforming raw data into a form suitable for downstream purposes like analytics.
    • Data processing involves collecting, processing, manipulating and managing data to extract meaningful information for end-users.
      • Data originates from diverse sources (transactions, observations, etc.)
      • Begins with data capture.
      • Two primary types: centralized and distributed.
    • Data processing cycle includes capturing, classifying, sort/merge, mathematical operations, transformation, archival, storage, retrieval, format, and present/governance.
    • Data munging steps:
      • Access: extracting raw data from the source.
      • Transform: manipulating raw data using algorithms (e.g., sorting, parsing) into specified structures.
      • Publish: depositing transformed data into a data sink for storage and future use.
    • Parallel data processing involves simultaneous execution of multiple sub-tasks that work together to complete a larger task.
    • Achieved by dividing a complex task into smaller, manageable parts that run concurrently.
    • Distributed data processing distributes tasks across several interconnected machines (cluster) for quicker and more efficient processing.
    • Processing workloads are categorized into:
      • Batch processing: offline processing of large data volumes, often resulting in high-latency responses.
        • Characterized by sequential read/write operations, often involving complex queries with multiple joins.
      • Transactional processing: online processing involving small data volumes with random read/write operations, resulting in low-latency.
        • Focus mainly on write-intensive operations.
    • Clusters enable distributed data processing with linear scalability.
      • Allow splitting large datasets into smaller ones for faster processing in parallel.
      • Can use batch or real-time processing modes.
      • Use low-cost commodity nodes for collective increased processing capacity.
      • Offer redundancy and fault tolerance for resilience.
    • MapReduce is a batch processing framework known for its scalability and reliability.
      • Follows the principle of divide-and-conquer for processing big data by distributing the data into smaller parts for processing in parallel.
    • MapReduce job processes data through map and reduce tasks.
    • MapReduce tasks involve splitting, mapping, shuffling, reducing, and providing final results..
    • Real-time processing (in-memory processing) involves capturing and processing data before persistence to disk, for fast sub-second to minute responses.
    • Characterized by high-velocity data and small data sizes.
    • Addresses velocity characteristic. Also called event or stream processing.
    • Data locality minimizes network congestion in Hadoop by placing computations close to where the data is residing, improving throughput.
    • Optimization techniques for Hadoop include proper cluster configuration, LZO compression, tuning MapReduce tasks, combiners, appropriate writable types, and reusing Writables.
    • Apache Spark, a prominent real-time processing framework, generally outperforms MapReduce for 100TB data sort.
    • Spark runtime performance on sorting data is much better than MapReduce.

    Spark and RDDs (Resilient Distributed Datasets)

    • Spark's core concept is RDD, which is
      • a fault-tolerant collection of elements.
      • processed in parallel.
    • RDDs are immutable, lazy-evaluated and are generally stored in-memory and partitioned across nodes, enabling parallel processing and location-aware processing, and are typed.
    • RDDs provide an abstraction that simplifies parallel processing.

    MapReduce vs. Spark

    • MapReduce is a batch-oriented processing framework.
    • Spark is designed for real-time processing and outperforms MapReduce in many cases, particularly when dealing with large datasets.

    Hadoop Scalability and High Availability

    • Hadoop's scalability refers to the ability to expand or contract the cluster easily.
    • Vertical scaling involves adding disks to nodes.
    • Horizontal scaling adds more nodes to the cluster without downtime, a distinctive feature of Hadoop.
    • Hadoop high availability architecture addresses single points of failure in the master node (NameNode) to ensure cluster availability and reliability even during failures.

    Hadoop Fault Tolerance

    • Hadoop Fault tolerance refers to the ability of the system to function despite failures of individual components.
    • Hadoop's fault-tolerance features rely on replicating data across multiple machines.
    • If a node fails, the data is accessible from other nodes that replicate the data, minimizing any downtime.

    Hadoop Optimization Techniques

    • Optimizing Hadoop involves proper cluster configuration.
    • LZO compression is appropriate to reduce data volume and improve processing speeds.
    • Tuning MapReduce tasks, combiners, appropriate data types, and reuse of Writables are essential for efficient performance.

    Real-World Applications

    • Financial services, retail, energy, and telecommunication industries often use Hadoop for data analytics and risk assessments to support decision-making and business growth.

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