Wednesday 5 April 2017

Namenode

Namenode

Name node,
    • What it stores
    • What it not stores
    • What is the responsible
    • How many name nodes
    • Production environment
    • If heart fails then what the result
    • Why Name node is high-expensive 
Stores
  • Name node is a master daemon, it is the heart of HDFS file system.
  • Name node stores the all files information’s which presents in HDFS. 
  • This file information we can say metadata as well, means Namenode stores the metadata about the files. 
  • Namenode is the point of contact for any hadoop files
Not stores
  • Namenode not stores raw data or actual data. 
Responsible 
  • We know file blocks are stored in Data Nodes, these data nodes maintains and manage by NameNode.
  • Client application communicates to name node to do file operations like add, copy, move, delete file.
  • Name node used to provide the required metadata to client.
How many
  • Only one name node per cluster.
Production
  • In production environment name node runs on separate machine.
If Namenode fails
  • As per the discussion Namenode is the heart of the HDFS, so if heart fails then we know well about the next condition.
  • Name node is a single point of failure, means if name node fails then accessing file system is not at all possible. 
Why Namenode is high expensive
  • Namenode should run in high end machine.
  • Reason why Namenode high expensive
    • Name node is a Single Point of Failure. (SPOF) 
    • Namenode holds metadata for quick response, so more memory is required.
    • Name node organizes hundreds or thousands of data nodes and respond to client requests.
    • Name node have to maintain load balance, by considering all reasons, name node required high expensive machine.
    • Based on requirement we can scaled-up machine for a name node.
Thanks for your time. 
Nireekshan