HBase comes integrated with Zoo keeper. When I start HBase, Zoo keeper instance is also started. The reason is that the Zoo keeper helps us in keeping a track of all region servers that are there for HBase. Zoo keeper keeps track of how many region servers are there, which region servers are holding from which DATA node to which data node. It keeps track of smaller data SETS where Hadoop is missing out. It decreases the overhead on top of Hadoop which keeps track of most of your META data. Hence HMaster gets the DETAILS of region servers by actually contacting Zoo keeper.

HBase comes integrated with Zoo keeper. When I start HBase, Zoo keeper instance is also started. The reason is that the Zoo keeper helps us in keeping a track of all region servers that are there for HBase. Zoo keeper keeps track of how many region servers are there, which region servers are holding from which data node to which data node. It keeps track of smaller data sets where Hadoop is missing out. It decreases the overhead on top of Hadoop which keeps track of most of your Meta data. Hence HMaster gets the details of region servers by actually contacting Zoo keeper.