What is HDFS block size and what did you chose in your project?
How to configure hadoop to reuse JVM for mappers?
Explain InputFormat?
Are Namenode and job tracker on the same host?
How will format the HDFS ?
What are combiners and its purpose?
Why we cannot do aggregation (addition) in a mapper? Why we require reducer for that?
What is the communication channel between client and namenode/datanode?
What is speculative execution in Hadoop?
What is crontab? Explain with suitable example?
What is the functionality of jobtracker in hadoop?
What happens in a textinputformat?
Explain the difference between NameNode