There is nothing sacred about electrons being called negative charge and protons positive charge.Itâs just a convention. You, can very well call electrons as positive charge and protons as negative charge!
Single Node or Psuedo-Distributed Cluster is the one in which all the essential daemons (like NameNode, DataNode, JobTracker and TaskTracker) run on the same machine. The default replication factor for a single node cluster is 1. A single node cluster is basically used to simulate a full cluster like environment and to test hadoop applications and unlike the Stand-alone mode, HDFS is accessible in this.
Companies implementing a Hadoop cluster generally choose one of the commercial distributions of the big data framework, which poses maintenance and support costs. Typically, it also must be used in coordination with a range of complementary technologies from what is referred to as the Hadoop ecosystem.