1. Select the correct option.
A.directory where namenode stores its metadata, with default value ${hadoop.tmp.dir}/dfs/name.
B. directory where HDFS data blocks are stored, with default value ${hadoop.tmp.dir}/dfs/data.
C. directory where secondary namenode store its checkpoints, default value is ${hadoop.tmp.dir}/dfs/namesecondary.
D. All options are correct
Select the correct options.
A. fsimage file, also known as namespace image file, is the checkpoint of metadata in memory on the hard disk. It is a serialized format and cannot be directly modified on the hard disk.
B. When the file system client writes, it is first recorded in the edit log
C. Before each write operation succeeds, the modification log is synced to the file system.
D. All of the above.
What is the use of touchz command?
A. To create empty file
B. To create a directory
C. To delete directory
D. None of these.
Which command we can use for copy from local to hdfs?
A. copyFromLocal
B. Put
C. Both A B
D. None of these
We use chown command ________.
A. To delete a directory with all files
B. Change the ownership of a file or directory
C. We can change the group of the file or directory by using chown command.
D. None of these
How can we check the health of hdfs?
A. By using health command
B. By using fsck command
C. By using setrep command
D. None of these
We can change the group of the file or directory by using ______ command.
A. chown
B. fsck
C. chgrp
D. None of these
Select the correct option.
A. balancer : Run cluster balancing tools. Administrators can simply press Ctrl-C to stop the balancing process.
B. Hadoop jar : Run the jar file. Users can bundle their MapReduce code into a jar file and execute it using this command.
C. distcp : Common commands used to copy data within or between clusters (as the name implies: dist is distributed, distributed copy.)
D. All of the above.
Which command is used to copy files from local to hdfs?
A. copyFromLocal or put
B. copyToLocal
C. moveFrom Local
D. None of these
_____________ is the process of converting structured objects into byte streams for transmission over the network or writing to persistent storage.
A. Serialization
B. Deserialization
C. Compression
D. None of these
All serializable objects in Hadoop must implement _________ interface.
A. List
B. Set
C. Writable
D. Map
Select the correct option.
A. Gzip: split-NO , compression ratio- Very high
B. Lzo : split-no, compression ratio- higher
C. Snappy-split-yes, compression ration -higher.
D. None of these
Select the correct option about coding & decoding.
A. DEFLATE : org.apache.hadoop.io.compress.DefaultCodec
B. Gzip : org.apache.hadoop.io.compress.GzipCodec
C. bzip2 : org.apache.hadoop.io.compress.BZip2Codec
D. All of the above.
Select the correct option about MapFile.
A. MapFile files can be seen as SequenceFile files that store ordered key-value.
B. MapFile files ensure that key-value keys are ordered (key-based).
C. Both A B are true
D. None of these
Main Features of Hadoop serialization are _________.
A. Extensible
B. Interoperable
C. Writable and fast
D. All of the above.
Select the correct option about MapReduce.
A. MapReduce is a high performance Cluster Computing Infrastructure based on clusters.
B. MapReduce is a Software Framework for parallel computing and running.
C. MapReduce is a parallel programming model that implements basic parallel computing tasks with two functions: Map and Reduce.
D. All of the above.
What is the use of Combiner phase?
A. Combiner is a localized Reduce operation.
B. it is the Map operation follow-up operations, mainly in the middle of the Map to calculate the file before doing a simple merge duplicate key values of operation
C. Combiner input does not affect to Reduce calculation final input, such as:If the calculation is only for the total, maximum and minimum values, you can use Combiner, but if you do the average calculation using Combiner, the final Reduce calculation result will be wrong.
D. All of the above.
Select the steps used in submitting a job.
A. The Job method uses the waitForCompletion method to submit a Job.
B. Apply for a JobID object from the ResourceManager of Yarn through RPC.
C. Obtain the authentication Token from HDFS NameNode and place it in the cache.
D. All of the above.
Select the correct steps in YARN Operation Process.
A. ResourceManager assigns the first Container to the application, communicates with the corresponding nod-manager (in heartbeat mode), and asks the Manager to start ApplicationMaster in this Container.
B. ApplicationMaster registers with ResourceManager so that users can view the running status of applications through ResourceManage.
C. ApplicationMaster applies for and obtains resources from ResourceManager through RPC in polling mode.
D. All of the above.
Select the correct statement about Partitioner.
A. Partitioner needs to determine how to properly allocate Mapper output to the Reducer
B. A custom Partitioner must implement the Partitioner interface and implement two core methods: getPartition() and configure().
C. Both A B
D. None of the above.
Select the correct option about Map Output format.
A. TextOutputFormat: output to a plain text file in the format of key + + value.
B. NullOutputFormat, /dev/null in Hadoop, sends the output to the black hole.
C. SequenceFileOutputFormat, output to sequence file format files.
D. All of the above.
Select the correct option.
A. Each map task is divided into the following stages: record reader, mapper, combiner, partitioner.
B. The output of the Map task is called intermediate data, including keys and values, which are sent to the reduce side.
C. Reduce tasks are divided into the following stages: shuffle, sort, reduce, output format.
D. All of the above.
Select the correct option.
A. The Record reader will translate the input fragments generated from input format into records.
B. In the Map phase, the user code is executed for each key-value pair processed from the record reader.
C. Combiner is a map stage grouping data, optional, local reducer.
D. All of the above.
Select the correct option.
A. Partitioner will get the key-value pairs from the mapper (or combiner) and split the slices, one for each reducer.
B. The Reduce task starts in the shuffle and sort phases. This stage gets the output file of the partitioner and downloads it to the local machine where the reduce runs.
C. The Reduce task takes the grouped data as input and executes the reduce method code for each key group.
D. All of the above.
MapReduce maximum, minimum, count calculation is equivalent to.
A. select max(num),min(num),count(*) from table group by condition
B. SELECT DISTINCT * FROM table;
C. Both A B
D. None of these