Namenode (Master)
Master responsible for co-ordination
Stores only the metadata
Default only 1 (Single Point of Failure)
High Availability
Secondary Namenode (Cold Backup)
Can be set manually as well
Datanode (Slave)
Horizontal Scalability (Can have as much as needed) (>35000)
Stores data
3 secs → TCP signal to Namenode (Heart Beat)
No reply in 10 min (Deadnode)
Types of Clusters
Single Node Setup
All 5 demons on the same node)
Pseudo Distributed Environment
Each daemon runs in a separate VM
Multi-node Cluster
Each daemon in separate node