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Message-ID: <12365988.188381288671446048.JavaMail.jira@thor>
Date: Tue, 2 Nov 2010 00:17:26 -0400 (EDT)
From: "Lu Yilei (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Subject: [jira] Commented: (HDFS-1458) Improve checkpoint performance by
 avoiding unnecessary image downloads
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    [ https://issues.apache.org/jira/browse/HDFS-1458?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12927292#action_12927292 ] 

Lu Yilei commented on HDFS-1458:
--------------------------------

To Hairong.
Thanks your good idea.
1. We can generate a UUID when SNN save fsimage. And we can add new fields for the UUID. If the UUID of the NameNode is equal the UUID of the SNN, we can't download the fsimage of NameNode.
2. Can checksum be returned with rollEditLog? Yes.

> Improve checkpoint performance by avoiding unnecessary image downloads
> ----------------------------------------------------------------------
>
>                 Key: HDFS-1458
>                 URL: https://issues.apache.org/jira/browse/HDFS-1458
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>    Affects Versions: 0.22.0
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.22.0
>
>         Attachments: checkpoint-checkfsimageissame.patch
>
>
> If secondary namenode could verify that the image it has on its disk is the same as the one in the primary NameNode, it could skip downloading the image from the primary NN, thus completely eliminating the image download overhead.

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