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From "Hairong Kuang (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-5034) NameNode should send both replication and deletion requests to DataNode in one reply to a heartbeat
Date Mon, 02 Feb 2009 19:17:59 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-5034?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Hairong Kuang updated HADOOP-5034:
----------------------------------

      Resolution: Fixed
    Release Note: This patch changes the DatanodeProtocoal version number from 18 to 19. The
patch allows NameNode to send both block replication and deletion request to a DataNode in
response to a heartbeat.
          Status: Resolved  (was: Patch Available)

I've just committed this.

> NameNode should send both replication and deletion requests to DataNode in one reply
to a heartbeat
> ---------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-5034
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5034
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: dfs
>    Affects Versions: 0.18.0
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.19.1
>
>         Attachments: blockTransferInvalidate.patch, blockTransferInvalidate1.patch, blockTransferInvalidate2.patch,
blockTransferInvalidate3.patch
>
>
> Currently NameNode favors block replication requests over deletion requests. On reply
to a heartbeat, NameNode does not send a block deletion request unless there is no block replication
request. 
> This brings a problem when a near-full cluster loses a bunch of DataNodes. In react to
the DataNode loss, NameNode starts to replicate blocks. However, replication takes a lot of
cpu and a lot of replications fail because of the lack of disk space. So the administrator
tries to delete some DFS files to free up space. However, block deletion requests get delayed
for very long time because it takes a long time to drain the block replication requests for
most DataNodes.
> I'd like to propose to let NameNode to send both replication requests and deletion requests
to DataNodes in one reply to a heartbeat. This also implies that the replication monitor should
schedule both replication and deletion work in one iteration.

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