The OpenStack Hadoop cluster, or Sahara, enables you to create a Hadoop cluster in your OpenStack environment. Sahara supports the following Hadoop-related solutions: Apache Hadoop, Hortonworks Data Platform (HDP), Cloudera Hadoop Distribution (CDH), Apache Spark, and MapR.
Fuel deploys HAProxy to provide load balancing, proxying, and high availability for OpenStack services. Each OpenStack controller runs HAProxy, which manages a single External Virtual IP (VIP) for all controller nodes and provides HTTP and TCP load balancing of requests going to OpenStack API services, RabbitMQ, and MySQL.
High Availability, or HA, is an approach to system infrastructure architecture that replicates servers and services to minimize downtime and data loss in the event of a hardware failure. To achieve high availability you must configure at least three controller nodes in your OpenStack environment.
A hypervisor is a virtualization platform that enables system administrators to create and manage virtual machines. OpenStack runs a hypervisor as a component of the compute node.