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https://issues.apache.org/jira/browse/HADOOP-227?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12462695
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dhruba borthakur commented on HADOOP-227:
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I am trying to come up with the default values for the following configurable
parameters:
1. The size of the edit log that can cause the next checkpoint.
2. The time period from one checkpoint to the other.
The next periodic checkpoint occurs whenever at least one of the above
conditions are met.
Assuming that a transaction takes 200 bytes in the edits log and the rate of
100 transactions per second, the edit log will increase at the rate of about
70MB per hour. Thus I am proposing that the default values for periodic
checkpoints be
1. edit log size = 64KB
2. time = 1hour
Comments appreciated.
> 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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