Datanode

Datanode

Data node,

• What it stores
• What is the responsible
• Heartbeats
  
• Block report
• How many
• Commission
• Decommission 
• Communication
• If data node fails

Store 

• A data node stores the actual data or raw data. 

Responsible 

• DataNode manages the blocks and store data blocks 
• DataNode responds to NameNode for any kind of file operations. 
• Data nodes takes responsible for serving read and write request for the clients. 

Heartbeat

• By using heartbeat mechanism data node used to update current status to NameNode about, 
• Stored blocks. 
• Idle blocks.
• Working status

• Heartbeat interval is every 3 seconds
• If heartbeat is not receiving then name node recognize particular data node down.
• When data node down then immediately name node takes responsible to take the replication of data. 

Block report

• Every 10th heart beat is a block report.

How many 

• It can be any number of data nodes per cluster, means if data set is growing then we can add more data nodes.

Commission 

• Adding Data Nodes to the cluster is called commissioning

Decommission 

• Removing Data Nodes from the cluster is called Decommissioning

Communication 

• One DataNode can communicate with other DataNode during replication 

If Data node fails

• When data node down or fails then immediately name node takes responsible to take the replication of data.

Thanks for your time. 

Nireekshan