Q18Big Data Analytics

HDFS is designed to reliably store massive datasets on commodity hardware. Its architecture includes the NameNode (metadata manager) and DataNodes (block storage). Fault Tolerance Mechanisms: 1. Data Replication: Every data block is replicated across multiple DataNodes (default replication factor is 3). If a node fails, the NameNode detects it and initiates replication of the lost blocks from the surviving replicas to other nodes. 2. Heartbeats and Block Reports: DataNodes send periodic heartbeats to the NameNode. If a heartbeat is not received within a specific time, the node is marked dead. Block reports inform the NameNode about the blocks held by a DataNode. 3. High Availability (HA): In modern Hadoop, an active/standby NameNode setup ensures that if the active NameNode fails, the standby takes over instantly using shared edit logs maintained by JournalNodes.