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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3329) DatanodeDescriptor objects stored in FSImage may be out dated.
Date Tue, 06 May 2008 06:09:55 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3329?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12594481#action_12594481
] 

dhruba borthakur commented on HADOOP-3329:
------------------------------------------

I think it is worthwhile to *not* store the DatanodeDescriptor in the fsimage at all. The
"append" code needs the location of the last block of the file to do lease recovery. In the
case when the namenode restarts and before it does lease recovery, it will get the block locations
of the last block from datanodes as part of block reports. 

> DatanodeDescriptor objects stored in FSImage may be out dated.
> --------------------------------------------------------------
>
>                 Key: HADOOP-3329
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3329
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: dfs
>            Reporter: Tsz Wo (Nicholas), SZE
>
> INodeFileUnderConstruction.targets is a DatanodeDescriptor array which stores the locations
for last block.  These DatanodeDescriptors are serialized and stored in the FSImage.  However,
a DatanodeDescriptor contains information like IP address and ports.  These information may
be out dated after a datanode restart.
> We should probably only stored the storageID of a DatanodeDescriptor in FSImage and then
lookup the DatanodeDescriptor object from the datanodeMap.

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