What is rack awareness in hadoop?

524

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While starting hadoop services, datanode service is not running?

486

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what happens when namenode goes down during file read operation in hadoop?

641

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Why slaves limited to 4000 in hadoop version 1?

535

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What is heartbeat in hadoop?

460

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Explain small file problem in hadoop

460

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How to create the directory when name node is in safe mode?

605

---

Why can we not create directory /user/dataflair/inpdata001 when name node is in safe mode?

485

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Ideally what should be the block size in hadoop?

496

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What happen when namenode enters in safemode in hadoop?

472

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What is shuffleing in mapreduce?

699

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Does mapreduce programming model provide a way for reducers to communicate with each other? In a mapreduce job can a reducer communicate with another reducer?

725

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How would you tackle calculating the number of unique visitors for each hour by mining a huge apache log? You can use post processing on the output of the mapreduce job.

897

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Describe what happens to a mapreduce job from submission to output?

726

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If reducers do not start before all mappers finish then why does the progress on mapreduce job shows something like map(50%) reduce(10%)? Why reducers progress percentage is displayed when mapper is not finished yet?

764

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