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https://issues.apache.org/jira/browse/HADOOP-2585?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Konstantin Shvachko updated HADOOP-2585:
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Hadoop Flags: [Reviewed]
Status: Patch Available (was: Open)
> Automatic namespace recovery from the secondary image.
> ------------------------------------------------------
>
> Key: HADOOP-2585
> URL: https://issues.apache.org/jira/browse/HADOOP-2585
> Project: Hadoop Core
> Issue Type: New Feature
> Components: dfs
> Affects Versions: 0.16.0
> Reporter: Konstantin Shvachko
> Assignee: Konstantin Shvachko
> Fix For: 0.18.0
>
> Attachments: SecondaryStorage.patch, SecondaryStorage.patch,
> SecondaryStorage.patch
>
>
> Hadoop has a three way (configuration controlled) protection from loosing the
> namespace image.
> # image can be replicated on different hard-drives of the same node;
> # image can be replicated on a nfs mounted drive on an independent node;
> # a stale replica of the image is created during periodic checkpointing and
> stored on the secondary name-node.
> Currently during startup the name-node examines all configured storage
> directories, selects the
> most up to date image, reads it, merges with the corresponding edits, and
> writes to the new image back
> into all storage directories. Everything is done automatically.
> If due to multiple hardware failures none of those images on mounted hard
> drives (local or remote)
> are available the secondary image although stale (up to one hour old by
> default) can be still
> used in order to recover the majority of the file system data.
> Currently one can reconstruct a valid name-node image from the secondary one
> manually.
> It would be nice to support an automatic recovery.
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