Answer / Shishir Mishra

Hadoop achieves fault tolerance through data replication and task redundancy. Data is distributed across multiple nodes, and each block of data is replicated across multiple nodes. If a node fails, another node with the same data can take over.

Why is Data Block size set to 128 MB in Hadoop?

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Why Hadoop performs replication, although it results in data redundancy?

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Clarify what a task tracker is in hadoop?

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What are some typical functions of Job Tracker?

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What is the purpose of context object?

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How can one write custom record reader?

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Suppose hadoop spawned 100 tasks for a job and one of the tasks failed. What will hadoop do?

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What does rack awareness mean?

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Web-ui shows that half of the datanodes are in decommissioning mode. What does that mean? Is it safe to remove those nodes from the network?

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List of some best tools that can be useful for data-analysis?

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What is Chain Mapper?

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What is Balancer in Hadoop?

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