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From: Apache Wiki <wikidiffs@apache.org>
To: core-commits@hadoop.apache.org
Date: Sat, 04 Apr 2009 17:50:10 -0000
Message-ID: <20090404175010.10569.94110@aurora.apache.org>
Subject: [Hadoop Wiki] Trivial Update of "Hbase/DesignOverview" by
 EvgenyRyabitskiy

Dear Wiki user,

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The following page has been changed by EvgenyRyabitskiy:
http://wiki.apache.org/hadoop/Hbase/DesignOverview

------------------------------------------------------------------------------
  
  HBase is an [http://apache.org/ Apache] open source project whose goal is to provide Bigtable-like storage for the Hadoop Distributed Computing Environment. HBase leverages the distributed data storage provided by the [http://hadoop.apache.org/core/docs/current/hdfs_design.html Hadoop Distributed File System (HDFS)] and use [http://hadoop.apache.org/zookeeper/docs/current/zookeeperOver.html ZooKeeper] for coordination between HBase nodes.
  
- Data is logically organized into tables, rows and columns.  An iterator-like interface is available for scanning through a row range and, of course, there is the ability to retrieve a column value for a specific row key. Any particular column may have multiple versions for the same row key.
+ Data is logically organized into tables, rows and columns. An iterator-like interface is available for scanning through a row range and, of course, there is the ability to retrieve a column value for a specific row key. Any particular column may have multiple versions for the same row key.
  
  [[Anchor(datamodel)]]
  = Data Model =
@@ -115, +115 @@

  [[Anchor(master)]]
  == HMaster ==
  
- There is only one HMaster for a single HBase deployment.
+ There is only one HMaster for a single HBase deployment. To ensure that there is always one active HMaster uses [http://hadoop.apache.org/zookeeper/docs/current/recipes.html#sc_leaderElection leader election algorithm] and it's address is stored in !ZooKeaper.
  
  HMaster duties:
  
@@ -123, +123 @@

   * Assigning/unassigning regions to/from H!RegionServers (unassigning is for load balance)
   * Monitor the health of each H!RegionServer
   * Changes to the table schema and handling table administrative functions
+ 
+ == Cluster initialization ==
+ 
+ 
  
  === Assigning regions to HRegionServers ===