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https://issues.apache.org/jira/browse/HADOOP-227?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12463466
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dhruba borthakur commented on HADOOP-227:
-----------------------------------------
This incorporates most review comments.
The main changes in this round of changes were in the following areas:
1. Handle error cases when one namedir is bad.
2. Use the fstime file to locate the latest and greatest edits file and image
file
3. Change the saveFSImage() function to use the code from periodic checkpoint.
This reduces code complexity because two different code paths need not be
maintained.
4. Uses Enums for image file names.
5. "format"ing creates an image and an empty editslog.
6. The TestCheckpoint simulates various namenode failure cases.
> Namespace check pointing is not performed until the namenode restarts.
> ----------------------------------------------------------------------
>
> Key: HADOOP-227
> URL: https://issues.apache.org/jira/browse/HADOOP-227
> Project: Hadoop
> Issue Type: Bug
> Components: dfs
> Affects Versions: 0.2.0
> Reporter: Konstantin Shvachko
> Assigned To: dhruba borthakur
> Attachments: patch-async-checkpoints-0.9.0,
> patch-async-checkpoints-0.9.0, patch-async-checkpoints-0.9.0,
> periodiccheckpoint.patch, periodiccheckpoint2.patch,
> periodiccheckpoint3.patch, periodiccheckpoint4.patch
>
>
> In current implementation when the name node starts, it reads its image file,
> then
> the edits file, and then saves the updated image back into the image file.
> The image file is never updated after that.
> In order to provide the system reliability reliability the namespace
> information should
> be check pointed periodically, and the edits file should be kept relatively
> small.
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