In Hadoop, which component is responsible for storing data across the machines of a cluster?
- A.MapReduce
- B.HDFS
- C.YARN
- D.Hive
Correct answer
Explanation
The correct answer is B, HDFS, the Hadoop Distributed File System. It splits a large file into fixed-size blocks, 128 megabytes by default in current versions, scatters those blocks over the machines of the cluster and keeps more than one copy of each block so that the failure of a machine does not lose data. A NameNode holds the directory of blocks while DataNodes hold the blocks themselves. Option A is wrong because MapReduce is the processing model, which works in a map stage and then a reduce stage on data already stored in HDFS. Option C is wrong because YARN, Yet Another Resource Negotiator, allots processing resources to jobs in the cluster and schedules them. Option D is wrong because Hive is a layer above Hadoop that lets a user run SQL-like queries, translating them into jobs underneath.
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Practice Questions
View allA central repository of information that can be analyzed to make more informed decisions is known as:
- A.Data mining
- B.Data storing
- C.Data sorting
- D.Data warehouse
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A data warehouse is exactly that, a central store into which data from many operational systems is extracted, cleaned and loaded so that it can be analysed for decision making.
Read the full explanation →Which of the following statement(s) is/are correct regarding On-Line Transaction Processing (OLTP)? I. Responses to the user inquiry are immediate. II. The associated cost is economical with efficient utilization of resources. III. The database is always up-to-date.
- A.Only II
- B.I and III
- C.I and II
- D.Only III
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On-Line Transaction Processing is the mode in which a bank counter, a railway booking window or a payment gateway works: each transaction is processed the moment it is entered, so the response to the user is immediate, and every committed transaction is written at once, so the database always reflects…
Read the full explanation →Which of the following is NOT one of the three Vs of big data?
- A.Volume
- B.Velocity
- C.Variety
- D.Virtualisation
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Virtualisation is the technique of running several logical machines on one physical machine and belongs to the chapter on cloud computing, not to the definition of big data.
Read the full explanation →Data mining is best described as which step of the knowledge discovery process?
- A.The collection of raw data from sensors
- B.The step that finds patterns in prepared data
- C.The backing up of a database
- D.The printing of a management report
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In the process called Knowledge Discovery in Databases, or KDD, the stages run from selection of the relevant data, through cleaning and preprocessing, to transformation, then data mining, and finally interpretation and evaluation of what was found.
Read the full explanation →Which algorithm is most closely associated with association rule mining and market basket analysis?
- A.Apriori
- B.k-means
- C.Dijkstra
- D.Quicksort
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The Apriori algorithm first finds the sets of items that appear together often enough to pass a support threshold, using the rule that any subset of a frequent set must itself be frequent, and then turns those frequent sets into rules measured by confidence.
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