Question - In what all modes can Hadoop be run?
Answer -
Hadoop can be run in three modes:
Standalone Mode: The default mode of Hadoop, standalone mode uses a local file system for input and output operations. This mode is mainly used for debugging purposes, and it does not support the use of HDFS. Further, in this mode, there is no custom configuration required for mapred-site.xml, core-site.xml, and hdfs-site.xml files. This mode works much faster when compared to other modes.
Pseudo-distributed Mode (Single-node Cluster): In the case of pseudo-distributed mode, you need the configuration for all the three files mentioned above. All daemons are running on one node; thus, both master and slave nodes are the same.
Fully distributed mode (Multi-node Cluster): This is the production phase of Hadoop, what it is known for, where data is used and distributed across several nodes on a Hadoop cluster. Separate nodes are allotted as master and slave nodes.