YARN acts as the operating system for Hadoop clusters by separating resource management from job scheduling and monitoring, allowing multiple data processing engines like MapReduce, Spark, Hive, and others to run simultaneously on the same cluster.
A DataNode in Hadoop is a worker node in the Hadoop Distributed File System (HDFS) that stores the actual data blocks and serves read/write requests from clients. DataNodes communicate regularly with the NameNode through heartbeat messages to report their health status and the blocks they're storing.
They handle data replication by creating multiple copies of blocks across different nodes to ensure fault tolerance, and they perform block verification to detect corruption. DataNodes also participate in data pipeline operations during file writes and coordinate with other DataNodes to maintain data integrity and availability across the distributed cluster.
