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The Ultimate Cheat Sheet On Hadoop

Top 20 frequently asked questions to test your Hadoop knowledge given in the below Hadoop cheat sheet. Try finding your own answers and match the answers given here.




Question #1 

You have written a MapReduce job that will process 500 million input records and generate 500 million key-value pairs. The data is not uniformly distributed. Your MapReduce job will create a significant amount of intermediate data that it needs to transfer between mappers and reducers which is a potential bottleneck. A custom implementation of which of the following interfaces is most likely to reduce the amount of intermediate data transferred across the network?



A. Writable
B. WritableComparable
C. InputFormat
D. OutputFormat
E. Combiner
F. Partitioner
Ans: e




Question #2 

Where is Hive metastore stored by default ?


A. In HDFS
B. In client machine in the form of a flat file.
C. In client machine in a derby database
D. In lib directory of HADOOP_HOME, and requires HADOOP_CLASSPATH to be modified.
Ans: c




Question…

Data lake Repository You Need to Know About it

In DataLake data stored internally in a repository. You can say this format as a blob. The data in DataLake does not have a particular Schema or Format.

data lake repository  example
Photo Credit: Srini

SQL Database

  • Let us take a traditional database, here, a database design and Scheme are to be defined before you enter data. In data-lake, there is no format for this. It is like a dump. 
  • This dump you can send to Hadoop repository for data analysis. This repository can be incremental. Also, you can build a large database.

Data lake Vs Hadoop

Data-Lake is a dump of data with no format. There are many pre-formats required before it sends for analytics. One is data security and encryption. These techniques to be done before you send your data to Hadoop repository.

In real-time, Hadoop data analytics need lot other pre-processing of data required to proceed further.

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