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Explain how HDFS (Hadoop Distributed File System) stores data across nodes.

Spark/Big Datahard0.6 min readPremium
Frequency
Low
Asked at 1 company
Category
452
questions in Spark/Big Data
Difficulty Split
88E|81M|283H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
BCG
Key Concepts Tested
optimizationpartition
Expert AnswerPremium
129 wordsInterview-ready
**Why it matters**: At scale, design choices directly impact reliability, latency, and cost. Wrong decisions compound across jobs and teams. HDFS stores data by splitting files into blocks (default 128MB), replicating blocks (default 3x) across DataNodes. NameNode tracks block locations and metadata. Client writes to first replica; that node pipelines to others. Reads are from nearest replica. Rack awareness: spread replicas across racks for fault tolerance....
The complete answer continues with detailed implementation patterns, architectural trade-offs, and production-grade considerations. It covers performance optimization strategies, common pitfalls to avoid, and real-world examples from companies like BCG. The answer also includes follow-up discussion points that interviewers commonly explore.

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