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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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Robert Chansler updated HADOOP-2585:
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Release Note: Improved management of replicas of the name space image. If
all replicas on the Name Node are lost, the latest check point can be loaded
from the secondary Name Node. Use parameter "-importCheckpoint" and specify the
location with "fs.checkpoint.dir." The directory structure on the secondary
Name Node has changed to match the primary Name Node.
Hadoop Flags: [Incompatible change, Reviewed] (was: [Reviewed])
> 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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