CCA-500 Questions and Answers

The client queries the NameNode for the locations of the block, and reads all three copies. The first copy to complete transfer to the client is the one the client reads as part of hadoop’s speculative execution framework.

The client queries the NameNode for the locations of the block, and reads from the first location in the list it receives.

The client queries the NameNode for the locations of the block, and reads from a random location in the list it receives to eliminate network I/O loads by balancing which nodes it retrieves data from any given time.

The client queries the NameNode which retrieves the block from the nearest DataNode to the client then passes that block back to the client.

For a 1GB child heap size an io.sort.mb of 128 MB will always maximize memory to disk I/O

Increase the io.sort.mb to 1GB

Decrease the io.sort.mb value to 0

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.

The DataNode JVM on one host is not active

Because your under-replicated blocks count matches the Live Nodes, one node is dead, and your DFS Used % equals 0%, you can’t be certain that your cluster has all the data you’ve written it.

Your cluster has lost all HDFS data which had bocks stored on the dead DatNode

The HDFS cluster is in safe mode

They must be formatted as HDFS

They must be formatted as either ext3 or ext4

They may be formatted in any Linux file system

They must not be formatted - - HDFS will format the file system automatically