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From "Suresh Srinivas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2802) Support for RW/RO snapshots in HDFS
Date Mon, 22 Oct 2012 20:38:15 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2802?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13481758#comment-13481758
] 

Suresh Srinivas commented on HDFS-2802:
---------------------------------------

bq. This sort of fundamental design decision is not something that can be easily improved
incrementally. Copying huge portions of the working set, and then making that copying fast
and space efficient, should not be the goal. The goal should be to entirely avoid copying
huge portions of the working set.
That is the goal. Where I disagree is with the assertion that we cannot get to it starting
with a simple implementation. I would like to get the simple implementation done ASAP with
all the tests developed in parallel. Then we will change the implementation for better efficiency
both in time and space. Tests will help ensure the correctness of optimizations. 

We already have a bunch of ideas on how to do it. Some of those ideas are in the early prototype
that Hari has uploaded. HDFS-4103 has been created to allay these concerns that have been
repeatedly brought up to convey that it is goal of HDFS-2802 to have optimized snapshots.
Will update the design document as a part of that jira.
                
> Support for RW/RO snapshots in HDFS
> -----------------------------------
>
>                 Key: HDFS-2802
>                 URL: https://issues.apache.org/jira/browse/HDFS-2802
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: data-node, name-node
>            Reporter: Hari Mankude
>            Assignee: Hari Mankude
>         Attachments: snap.patch, snapshot-one-pager.pdf, Snapshots20121018.pdf
>
>
> Snapshots are point in time images of parts of the filesystem or the entire filesystem.
Snapshots can be a read-only or a read-write point in time copy of the filesystem. There are
several use cases for snapshots in HDFS. I will post a detailed write-up soon with with more
information.

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