Hadoop Interview Questions and Answers
11. What is commodity hardware?
Commodity Hardware refers to inexpensive systems that do not have high availability or high quality. Commodity Hardware consists of RAM because there are specific services that need to be executed on RAM. Hadoop can be run on any commodity hardware and does not require any super computer s or high end hardware configuration to execute jobs.
12. Explain what is heartbeat in HDFS?
Heartbeat is referred to a signal used between a data node and Name node, and between task tracker and job tracker, if the Name node or job tracker does not respond to the signal, then it is considered there is some issues with data node or task tracker.
13. What happens when a datanode fails ?
When a datanode fails Jobtracker and namenode detect the failure On the failed node all tasks are re‐scheduled Namenode replicates the users data to another node
14. Explain what happens in textinformat ?
In textinputformat, each line in the text file is a record.
Value is the content of the line while Key is the byte offset of the line.
For instance, Key: longWritable, Value: text
15. Explain what is sqoop in Hadoop?
To transfer the data between Relational database management (RDBMS) and Hadoop HDFS a tool is used known as Sqoop. Using Sqoop data can be transferred from RDMS like MySQL or Oracle into HDFS as well as exporting data from HDFS file to RDBMS.
16. Mention what are the data components used by Hadoop?
Data components used by Hadoop are
- Pig
- Hive
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