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https://issues.apache.org/jira/browse/HADOOP-227?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12464081
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Raghu Angadi commented on HADOOP-227:
-------------------------------------
regd 64MB default size, It need not be tailored so that it takes one hour to
reach the limit.. there is already other variable to do checkpoints every one
hour. As Sameer pointed out its size could be determined by how it affects
NameNode start up time. Since namenode start time depends more on the image
size, edits log size could be larger. A small value could have more burden on
NameNodes that are already busy. In a big deployment, default many not matter
at all since it will be manually set.
> 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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