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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1623) High Availability Framework for HDFS NN
Date Mon, 25 Jul 2011 18:01:12 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1623?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13070643#comment-13070643
] 

dhruba borthakur commented on HDFS-1623:
----------------------------------------

Hi Yang, The zk heartbeats and delivery of notifications is not inline with the HDFS writes
to its transaction logs. Assume a scenario where ZK delivers a disconnected event to NameNode,
but the NameNode already is in the midst of a flushing a long list of transactions to its
transaction logs. This could potentially take a non-trivial amount of time (process scheduling,
GC issues, etc).

Todd: what is our proposed solution for doing IO fencing on transaction logs that reside on
a NFS filer? Here we are proposing that we do the following before we can do an auto failover:

1. If the original NameNode is reachable, kill the original NameNode process and verify that
it is killed.
2. If step 1 fails (because of network connectivity issue), then issue a power-cycle event
to the original NameNode machine via its configured console port. Verify that machine is power-cycled.
3. If Step 2 fails, then abort auto failover. Otherwise continue failover sequence.

> High Availability Framework for HDFS NN
> ---------------------------------------
>
>                 Key: HDFS-1623
>                 URL: https://issues.apache.org/jira/browse/HDFS-1623
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>            Reporter: Sanjay Radia
>            Assignee: Sanjay Radia
>         Attachments: HDFS-High-Availability.pdf, NameNode HA_v2.pdf, NameNode HA_v2_1.pdf,
Namenode HA Framework.pdf
>
>


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