Hosting the Hadoop ecosystem

Often, additional Hadoop components are not hosted within the cluster itself. Most of these projects act as clients to HDFS and MapReduce and can be executed on separate servers. Such servers were marked as Hadoop clients, as shown in the cluster diagram from Chapter 1, Setting Up Hadoop Cluster – from Hardware to Distribution. The main reason for separating Hadoop nodes from clients physically and on a network level is security. Hadoop client servers are supposed to be accessed by different people within your organization. If you decide to run clients on the same servers as Hadoop, you will have to put in lots of effort providing a proper level of access to every user. Separating those instances logically and physically simplifies the task. Very often, Hadoop clients are deployed on virtual machines, since resource requirements are modest.

Note

Keep in mind those clients who read and write HDFS data need to be able to access NameNodes, as well as all DataNodes...