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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3631) Transfer of image from secondary name node should not interrupt service
Date Fri, 08 Aug 2008 05:31:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3631?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12620842#action_12620842
] 

dhruba borthakur commented on HADOOP-3631:
------------------------------------------

My proposal actually needs three disks irrespective of the number of namedirs. For starters,
the fsimage on all the namedirs will use D1, the edits file on all the namedirs will be on
D2 and the edits.new on all namedirs will be on D3.

Also, since edits and edits.new are on different disks, it is never the case that the Secondary
will read/write to the same disk on which the namenode is currently logging transactions.

> Transfer of image from secondary name node should not interrupt service
> -----------------------------------------------------------------------
>
>                 Key: HADOOP-3631
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3631
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: dfs
>    Affects Versions: 0.17.0
>            Reporter: Robert Chansler
>            Priority: Critical
>             Fix For: 0.19.0
>
>
> The transfer of the new image prepared by the secondary name node can interfere with
client services. Clients observe delays in completing RPCs. In general, administrative activities
should not be observed by the clients. For large clusters, administrators are reluctant to
run the secondary name node leading to excessive edit logs. (Excessive in the sense that if
the cluster must be restarted, a long time is required to process the log.)
> Maybe the new image does not have to be transfered; it could be fetched when needed.
> Maybe the priority of the transfer task can be reduced so that the transfer is not observed.
> Maybe a different transfer protocol is more appropriate.

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