1. Introduction 2. Quiz: Input Data How to find total sales/store? KEY VALUE * time store name * cost store name * store name cost * store name product type 3. Quiz: Defensive Mapper Code # Your task is to make sure that this mapper code does not fail on corrupt data lines, # but

1. Quiz: HDFS Which of the following is true? * HDFS uses a central SAN(storage area network) to hold its data * HDFS stores a single copy of all data * HDFS replicates all data for reliability * To store 100TB of data in a Hadoop cluster you would need 300TB of raw

1. Quiz: HDFS Is there a problem? > https://youtu.be/6F8-cCUbRU8 * Network failure * Disk failure on DN(datanode) * Not all DN used * Block sizes differ * Disk failure on NN(namenode) 2. Quiz: Data Redundancy Any problem now?(when NN failure) * Data inaccessible > when network failure on NN * Data

1. Quiz: Dimensions of Big Data Which of the following are Part of the 3 dimensions of Big Data? * Volume * Cost * Importance * Velocity * Source * Variety * Security * Virality 2. Quiz: Volume Volume of Big Data refers to: * Importance of Data * Size of data * Speed of data generation * The differnet data sources

1. Introduction You can read more about Big Data in Wikipedia which is also a company that generates and processes huge amounts of data itself. MapReduce and Apache Hadoop are the technologies we will be talking about more in this course. 2. Data Sources According to IBM: “Every day, 2.