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dhruba borthakur commented on HDFS-1972: ---------------------------------------- I recollect that we prevent primary namenode from issuing BLOCK_INVALIDATE commands for a particular datanode until the time it has received a full block report from that datanode (since the last failover event). But I will read proposal 3 in greater detail, > HA: Datanode fencing mechanism > ------------------------------ > > Key: HDFS-1972 > URL: https://issues.apache.org/jira/browse/HDFS-1972 > Project: Hadoop HDFS > Issue Type: Sub-task > Components: data-node, name-node > Reporter: Suresh Srinivas > Assignee: Todd Lipcon > > In high availability setup, with an active and standby namenode, there is a > possibility of two namenodes sending commands to the datanode. The datanode > must honor commands from only the active namenode and reject the commands > from standby, to prevent corruption. This invariant must be complied with > during fail over and other states such as split brain. This jira addresses > issues related to this, design of the solution and implementation. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa For more information on JIRA, see: http://www.atlassian.com/software/jira