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Why does Hadoop require running 'hdfs dfsadmin -refreshNodes' after modifying include or exclude files instead of automatically detecting changes?

hard📝 Conceptual Q10 of 15
Hadoop - Cluster Administration
Why does Hadoop require running 'hdfs dfsadmin -refreshNodes' after modifying include or exclude files instead of automatically detecting changes?
ABecause the exclude file is stored on DataNodes
BTo avoid performance overhead from constant file monitoring
CTo prevent accidental node removals
DBecause the NameNode cannot read files dynamically
Step-by-Step Solution
Solution:

  1. Step 1: Understand why manual refresh is needed

    Automatically monitoring files would cause extra load and reduce cluster performance.

  2. Step 2: Reason about design choice

    Manual refresh lets admins control when to apply changes, avoiding unnecessary overhead.

  3. Final Answer:

    To avoid performance overhead from constant file monitoring -> Option B

  4. Quick Check:

    Manual refresh avoids performance overhead [OK]
Quick Trick: Manual refresh avoids constant monitoring overhead [OK]
Common Mistakes:
  • Thinking NameNode cannot read files dynamically
  • Assuming refresh prevents accidental removals
  • Believing exclude file is stored on DataNodes

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