title: HBase HDFS zookeeper
body: <p>Now I am learning about HBase. I set up my HBase Cluster and Hadoop Cluster like this:</p>
  
  <pre><code>server1: Namenode HMaster
  server2: datanode1 RegionServer1 HQuorumPeer
  Server3: datanode2 RegionServer2 HQuorumPeer
  Server4: datanode3 RegionServer3 HQuorumPeer
  </code></pre>
  
  <p>I have several question about HBase cluster:</p>
  
  <pre><code>1: All RegionServers must be in the Hadoop Cluster so it can use HDFS to store 
     data, even though it will store data into local file system, right?
  2: What does RegionServer do? Does the HMaster give the job to all RegionServeres 
     and let them running parallel, like tasktracker in datanode? 
  3: What does zookeeper do? Do I need to setup zookeeper in all RegionServers 
     nodes and the master node? 
  4: It is related to #3. I know HBase uses zookeeper to recovery once regionServer 
     is down. How does it specific work?   
  </code></pre>