How does the NameNode detect that a DataNode has failed?

The NameNode uses RAM for the following purpose:

What is a Writable?

During the standard sort and shuffle phase of MapReduce, keys and values are passed to
reducers. Which of the following is true?

What is the behavior of the default partitioner?

Which statement best describes the data path of intermediate key-value pairs (i.e., output of the
mappers)?

If you run the word count MapReduce program with m mappers and r reducers, how many output
files will you get at the end of the job? And how many key-value pairs will there be in each file?
Assume k is the number of unique words in the input files.

You have a large dataset of key-value pairs, where the keys are strings, and the values are
integers. For each unique key, you want to identify the largest integer. In writing a MapReduce
program to accomplish this, can you take advantage of a combiner?

What happens in a MapReduce job when you set the number of reducers to zero?

Combiners Increase the efficiency of a MapReduce program because: