HDFS Architecture

HDFS Architecture

This architecture gives you a complete picture of HDFS. There is a single namenode which stores metadata and there are multiple datanodes which do actual storage work. Nodes are arranged in racks and Replicas of data blocks are stored on different racks in the cluster to provide fault tolerance. In remaining section of this tutorial we will see, how read and write operations are performed in HDFS? To read or write a file in HDFS, the client needs to interact with Namenode. HDFS applications need a write-once-read-many access model for files. A file once created and written cannot be edited.


 


Namenode stores metadata and datanode which stores actual data. The client interacts with namenode for any task to be performed as namenode is the centerpiece in the cluster.
There are several datanodes in the cluster which store HDFS data in the local disk. Datanode sends a heartbeat message to namenode periodically to indicate that it is alive. Also, it replicates data to other datanode as per the replication factor.