Several daemons for Hadoop

After installing Hadoop, there are a few processes that can be used with JPS.

In Master there are:

Namenode

Secondarynamenode

Jobtracker

There are slaves in the

Tasktracker

Datanode

1. NameNode

It is the primary server in Hadoop, which manages the file System namespace and access to files stored in the cluster.

2. Secondarynamenode

It is not a redundant daemon for namenode, but rather a periodic checkpoint and cleanup task.

For reasons of scalability and fault tolerance, we typically run Secondarynamenode on a non- NameNode machine.

3. DataNode

It is responsible for managing the storage that is connected to the node (multiple nodes can be in a cluster). Each node that stores data runs a Datanode daemon.

4 and 5. jobtracker and tasktracker

Jobtracker is responsible for dispatching the work on DataNode . Each DataNode has a tasktrackerthat performs the actual work.

jobtracker and tasktracker use master-form,jobtracker cross- DataNode distribution work, while Tasktracker perform the task.

Jobtracker also checks the requested work, and if a DataNode fails for any reason,Jobtracker will reschedule the previous task.

Several daemons for Hadoop