What two processes must you do if you are running a Hadoop cluster with a single NameNode and six DataNodes, and you want to change a configuration parameter so that it affects all six DataNodes.

• A. You must modify the configuration files on only one of the DataNode machine
• B. You don't need to restart any daemon, as they will pick up changes automatically.
• C. You must modify the configuration files on each of the six DataNode machines.
• D. You must modify the configuration files on the NameNode only. DataNodes read their configuration from the master nodes.
• E. You must restart the NameNode daemon to apply the changes to the cluster
• F. You must restart all six DataNode daemons to apply the changes to the cluster.

Which command does Hadoop offer to discover missing or corrupt HDFS data?

• A. Du
• B. Hadoop does not provide any tools to discover missing or corrupt data; there is no need because three replicas are kept for each data block.
• C. Fsck
• D. The map-only checksum utility,
• E. Dskchk

Your Hadoop cluster has 12 slave nodes, a block size set to 64MB, and a replication factor of three.
Choose which best describes how the Hadoop Framework distributes block writes into HDFS from a Reducer outputting a 150MB file?

• A. The Reducer will generate twelve blocks and write them to slave nodes nearest the node on which the Reducer runs.
• B. Reducers don't write blocks into HDFS
• C. The Reducer will generate nine blocks and write them randomly to nodes throughout the cluster.
• D. The slave node on which the Reducer runs gets the first copy of every block written. Other block replicas will be placed on other nodes.

You has a cluster running with the Fail Scheduler enabled. There are currently no jobs running on the cluster you submit a job A, so that only job A is running on the cluster. A while later, you submit job B.
Now job A and Job B are running on the cluster al the same time. How will the Fair' Scheduler handle these two Jobs?

• A. When job B gets submitted, it will get assigned tasks, while job A continues to run with fewer tasks.
• B. When job A gets submitted, it doesn't consume all the task slot
• C. When job B gets submitted, Job A has to finish first, before job it can get scheduled.
• D. When job A gets submitted, it consumes all the task slot

What happens when a map task crashes while running a mapreduce job?

• A. the jobtracket attempts to re-run the task on a different node
• B. The tasktracker closes the JVM instance and restarts
• C. The job immediately fails
• D. The jobtracker attempts to re-run the task on the same node