At work the other day, I was reading about Hadoop’s 5 daemons. The information wasn’t quite clicking, so I drew a picture to cement the concepts into my mind. (I’ve checked that all information regarding Hadoop in this blogpost is publicly available.)
In words:
Hadoop is comprised of five separate daemons. Each of these daemon runs in its own JVM.
The following 3 Daemons run on Master nodes:
- NameNode – This daemon stores and maintains the metadata for HDFS.
- Secondary NameNode – Performs housekeeping functions for the NameNode.
- JobTracker – Manages MapReduce jobs, distributes individual tasks to machines running the Task Tracker.
The following 2 Daemons run on Slave nodes:
- DataNode – Stores actual HDFS data blocks.
- TaskTracker – Responsible for instantiating and monitoring individual Map and Reduce tasks.
Hi
Do you know which process prepares the execution plan to fetch the data blocks from data nodes.
Thanks
Shyam
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