Resource Manager supports multiple hubs. A hub represents an instance of the zenhub daemon, through which all collector daemons communicate with the object and event databases. Hubs are associated with a resource pool, allowing for better collector distribution.
All collectors must belong to exactly one hub; however, many collectors can be associated with a hub. All hubs (and indirectly all collectors) refer to the same object and event databases. Typically, only very large systems with more than five collectors (or more than 1,500 devices) benefit from multiple hubs.
The ZooKeeper service on the HBase cluster maintains configuration data and provides distributed synchronization and group services.