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Data locality in Hadoop - explain

Spark/Big Dataeasy0.4 min readPremium
Frequency
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Asked at 1 company
Category
452
questions in Spark/Big Data
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88E|81M|283H
in this category
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1,863
across 7 categories
Asked at these companies
JP Morgan
Key Concepts Tested
spark
Expert AnswerPremium
83 wordsInterview-ready
**Why locality matters**: Running tasks where data lives reduces network transfer—critical when network << disk. **Mechanism**: HDFS stores blocks on DataNodes; MapReduce/Spark prefer to schedule tasks on nodes holding those blocks. Rack-local as fallback; off-rack as last resort. **Scalability trade-offs**: Good locality = faster; cloud storage (S3) has no locality—all reads are network....
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