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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3637) Support for snapshots
Date Thu, 28 Aug 2008 23:55:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3637?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12626797#action_12626797
] 

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

Just to clarify on Doug' comments:

>Perhaps snapshots should never be held in memory, but rather dealt with as an on-disk
datastructure? Thus it would be >possible to browse snapshots, but not very quickly.

We can come up with a plan to read snapshots directly from the disk image. However, the SnapNode
still has to exist  because it has to replicate blocks in the snapshot.

Once we have the ability to serve snapshot data directly from the fsimage on disk, the same
technique could be used to serve data from the primary namespace! But I plan to do it as a
separate JIRA as not as part of snapshots. Does it make sense?

> 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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