Shulou(Shulou.com)06/03 Report--

1 、 Namenode

Daemon for HDFS

How the file is divided into blocks when recording, and on which nodes these blocks are stored

Centralized management of memory and Icano

It is a single point, and failure will cause the cluster to crash.

2 、 Secondary Namenode

Secondary daemon that monitors the status of HDFS

Each cluster has one.

Communicate with NameNode to save HDFS metadata snapshots regularly

When NameNode fails, it can be used as a backup NameNode.

3 、 DataNode

Each slave server runs one

Responsible for reading and writing HDFS blocks to the local file system

4 、 JobTracker

Daemon for processing jobs (user submitted code)

Decide which files are involved in the processing, then cut the task and assign nodes

Monitor task and restart failed task (at different points)

There is only one JobTracker per cluster, which is located on the Master node

5 、 TaskTracker

Located on the slave node, combined with datanode (principles of code and data)

Manage task on their respective nodes (assigned by jobtracker)

There is only one tasktracker per node, but a tasktracker can start multiple JVM to execute map or reduce tasks in parallel

Interact with jobtracker

1. 6, Master and Slave

Master:Namenode 、 Secondary Namenode 、 jobtracker . Browser (for viewing the management interface), other Hadoop tools

Slave:Tasktracker 、 Datenode

Master is not the only one

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