Hortonworks Apache-Hadoop-Developer 問題集

質問 1：
Which one of the following statements is FALSE regarding the communication between DataNodes and a federation of NameNodes in Hadoop 2.0?
A. DataNodes send periodic heartbeats to all the NameNodes.
B. DataNodes send periodic block reports to all the NameNodes.
C. Each DataNode registers with all the NameNodes.
D. Each DataNode receives commands from one designated master NameNode.
正解：D

質問 2：
In a MapReduce job, the reducer receives all values associated with same key. Which statement best describes the ordering of these values?
A. The values are arbitrarily ordered, and the ordering may vary from run to run of the same MapReduce job.
B. The values are arbitrary ordered, but multiple runs of the same MapReduce job will always have the same ordering.
C. Since the values come from mapper outputs, the reducers will receive contiguous sections of sorted values.
D. The values are in sorted order.
正解：A
解説: (Topexam メンバーにのみ表示されます)

質問 3：
When is the earliest point at which the reduce method of a given Reducer can be called?
A. As soon as at least one mapper has finished processing its input split.
B. It depends on the InputFormat used for the job.
C. As soon as a mapper has emitted at least one record.
D. Not until all mappers have finished processing all records.
正解：D
解説: (Topexam メンバーにのみ表示されます)

質問 4：
You want to run Hadoop jobs on your development workstation for testing before you submit them to your production cluster. Which mode of operation in Hadoop allows you to most closely simulate a production cluster while using a single machine?
A. Run simldooop, the Apache open-source software for simulating Hadoop clusters.
B. Run all the nodes in your production cluster as virtual machines on your development workstation.
C. Run the hadoop command with the -jt local and the -fs file:///options.
D. Run the DataNode, TaskTracker, NameNode and JobTracker daemons on a single machine.
正解：D

質問 5：
What types of algorithms are difficult to express in MapReduce v1 (MRv1)?
A. Text analysis algorithms on large collections of unstructured text (e.g, Web crawls).
B. Large-scale graph algorithms that require one-step link traversal.
C. Algorithms that require global, sharing states.
D. Relational operations on large amounts of structured and semi-structured data.
E. Algorithms that require applying the same mathematical function to large numbers of individual binary records.
正解：C
解説: (Topexam メンバーにのみ表示されます)

質問 6：
You need to move a file titled "weblogs" into HDFS. When you try to copy the file, you can't. You know you have ample space on your DataNodes. Which action should you take to relieve this situation and store more files in HDFS?
A. Decrease the block size on all current files in HDFS.
B. Increase the block size on your remaining files.
C. Decrease the block size on your remaining files.
D. Increase the block size on all current files in HDFS.
E. Increase the number of disks (or size) for the NameNode.
F. Increase the amount of memory for the NameNode.
正解：C

質問 7：
Which describes how a client reads a file from HDFS?
A. The client queries all DataNodes in parallel. The DataNode that contains the requested data responds directly to the client. The client reads the data directly off the DataNode.
B. The client contacts the NameNode for the block location(s). The NameNode contacts the DataNode that holds the requested data block. Data is transferred from the DataNode to the NameNode, and then from the NameNode to the client.
C. The client queries the NameNode for the block location(s). The NameNode returns the block location(s) to the client. The client reads the data directory off the DataNode(s).
D. The client contacts the NameNode for the block location(s). The NameNode then queries the DataNodes for block locations. The DataNodes respond to the NameNode, and the NameNode redirects the client to the DataNode that holds the requested data block(s). The client then reads the data directly off the DataNode.
正解：C
解説: (Topexam メンバーにのみ表示されます)