Cloudera CCA-500 問題集

質問 1：
Which two are features of Hadoop's rack topology?
A. Hadoop gives preference to intra-rack data transfer in order to conserve bandwidth
B. Even for small clusters on a single rack, configuring rack awareness will improve performance
C. Rack location is considered in the HDFS block placement policy
D. Configuration of rack awareness is accomplished using a configuration file. You cannot use a rack topology script.
E. HDFS is rack aware but MapReduce daemon are not
正解：B,C

質問 2：
In CDH4 and later, which file contains a serialized form of all the directory and files inodes in the filesystem, giving the
NameNode a persistent checkpoint of the filesystem metadata?
A. Fsimage_N (where N reflects transactions up to transaction ID N)
B. Edits_N-M (where N-M transactions between transaction ID N and transaction ID N)
C. fstime
D. VERSION
正解：A
解説: (Topexam メンバーにのみ表示されます)

質問 3：
You suspect that your NameNode is incorrectly configured, and is swapping memory to disk. Which Linux commands
help you to identify whether swapping is occurring?
A. swapinfo
B. free
C. jps
D. memcat
E. vmstat
F. top
G. df
正解：B,E,F
解説: (Topexam メンバーにのみ表示されます)

質問 4：
Your Hadoop cluster contains nodes in three racks. You have not configured the dfs.hosts property in the NameNode's
configuration file. What results?
A. Any machine running the DataNode daemon can immediately join the cluster
B. Presented with a blank dfs.hosts property, the NameNode will permit DataNodes specified in mapred.hosts to join
the cluster
C. The NameNode will update the dfs.hosts property to include machines running the DataNode daemon on the next
NameNode reboot or with the command dfsadmin -refreshNodes
D. No new nodes can be added to the cluster until you specify them in the dfs.hosts file
正解：C

質問 5：
You're upgrading a Hadoop cluster from HDFS and MapReduce version 1 (MRv1) to one running HDFS and MapReduce
version 2 (MRv2) on YARN. You want to set and enforce version 1 (MRv1) to one running HDFS and MapReduce
version 2 (MRv2) on YARN. You want to set and enforce a block size of 128MB for all new files written to the cluster
after upgrade. What should you do?
A. Set dfs.block.size to 128 M on all the worker nodes and client machines, and set the parameter to final. You do not
need to set this value on the NameNode
B. You cannot enforce this, since client code can always override this value
C. Set dfs.block.size to 134217728 on all the worker nodes, on all client machines, and on the NameNode, and set the
parameter to final
D. Set dfs.block.size to 128M on all the worker nodes, on all client machines, and on the NameNode, and set the
parameter to final
E. Set dfs.block.size to 134217728 on all the worker nodes and client machines, and set the parameter to final. You do
not need to set this value on the NameNode
正解：A

質問 6：
You observed that the number of spilled records from Map tasks far exceeds the number of map output records. Your
child heap size is 1GB and your io.sort.mb value is set to 1000MB. How would you tune your io.sort.mb value to
achieve maximum memory to disk I/O ratio?
A. For a 1GB child heap size an io.sort.mb of 128 MB will always maximize memory to disk I/O
B. Tune the io.sort.mb value until you observe that the number of spilled records equals (or is as close to equals) the
number of map output records.
C. Increase the io.sort.mb to 1GB
D. Decrease the io.sort.mb value to 0
正解：B