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…

Question

Options

• AThe Reducer will generate twelve blocks and write them to slave nodes nearest the node on which
• BThe Reducer will generate nine blocks and write them randomly to nodes throughout the cluster.
• CThe slave node on which the Reducer runs gets the first copy of every block written. Other block replicas
• DReducers don't write blocks into HDFS

• A
  16% (7)
• B
  7% (3)
• C
  73% (33)
• D
  4% (2)

Explanation

*The placement of replicas is critical to HDFS reliability and performance. Optimizing replica placement distinguishes HDFS from most other distributed file systems. This is a feature that needs lots of tuning and experience. The purpose of a rack-aware replica placement policy is to improve data reliability, availability, and network bandwidth utilization. The current implementation for the replica placement policy is a first effort in this direction. The short-term goals of implementing this policy are to validate it on production systems, learn more about its behavior, and build a foundation to test and research more sophisticated policies. * In HDFS data is split into blocks and distributed across multiple nodes in the cluster. Each block is typically 64Mb or 128Mb in size. Each block is replicated multiple times. Default is to replicate each block three times. Replicas are stored on different nodes. HDFS utilizes the local file system to store each HDFS block as a separate file. HDFS Block size can not be compared with the traditional file system block size.

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