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https://issues.apache.org/jira/browse/HADOOP-227?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12463102
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Sameer Paranjpye commented on HADOOP-227:
-----------------------------------------
64KB seems aggressive, it only allows about 300 transactions before a
checkpoint happens. Checkpointing should be frequent enough that when the
namenode restarts it should be able to merge the edits into the namespace in a
fairly short period of time (10-15 seconds perhaps?).
It might be useful to monitor how many edits can be merged into the image in 10
seconds (on a 2Ghz CPU say) and use something around that as the default.
> 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
>
>
> 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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