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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3637) Support for snapshots
Date Fri, 05 Sep 2008 20:32:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3637?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12628732#action_12628732
] 

dhruba borthakur commented on HADOOP-3637:
------------------------------------------

Here are the suggestion modifications to my current proposal:

1. There should be an ability to specify the exclude list at snapshot creation time. It is
not enough to have a cluster-wide exclude list that apply to all snapshot-creations.
2. The SnapNode could merge the fsimage, fsedits and exclude list to create a single fsimage
(optimization).
3. When a block is managed by the NameNode as well as the SnapNode, who manages replication
for this block? The proposal is that the SnapNode forward all replication request to the NameNode.
The NameNode can look into its blockmap to decide whether this block really needs replication.
This simplifies the architecture because it is ways the NameNode who is the final arbitrator
of what to replicate. Similarly, if the SnapNode detects excess replicas fr a block, it forwards
the delete-excess-replica request to the NameNode. The NameNode, based on its own blockmap,
decides whether to delete the excess replica or not.
4. This design has not impact on Namespace quotas or disk quotas. Snapshots are created by
the system administrator and has no impact on per-directory bases disk quotas.

> Support for snapshots
> ---------------------
>
>                 Key: HADOOP-3637
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3637
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: dfs
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>         Attachments: Snapshots.pdf, Snapshots.pdf
>
>
> Support HDFS snapshots. It should support creating snapshots without shutting down the
file system. Snapshot creation should be lightweight and a typical system should be able to
support a few thousands concurrent snapshots. There should be a way to surface (i.e. mount)
a few of these snapshots simultaneously.

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