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From "Konstantin Shvachko (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1108) Log newly allocated blocks
Date Tue, 23 Aug 2011 22:49:30 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1108?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13089840#comment-13089840

Konstantin Shvachko commented on HDFS-1108:

Yes, two proposals. So let me ask you the same question I've been asking Suresh. Which proposal
are you implementing?
1) RPC based (BackupNode)
2) shared storage based (AvatarNode-like design)

As I understood Suresh is trying to build a universal HA framework applicable to both. Your
patch is intended for proposal 2 only and therefore contradicts his effort, if I am not missing
Is there a community decision on where we are going? Do we need to have a vote on this?

I consider the performance overhead for syncing on each addBlock() as a disadvantage of shared
storage based approach.

I think this issue should be blocked until the HA approach dilemma is resolved, as it attempts
to implicitly move development in one particular direction.

> Log newly allocated blocks
> --------------------------
>                 Key: HDFS-1108
>                 URL: https://issues.apache.org/jira/browse/HDFS-1108
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: name-node
>            Reporter: dhruba borthakur
>            Assignee: Todd Lipcon
>             Fix For: HA branch (HDFS-1623)
>         Attachments: HDFS-1108.patch, hdfs-1108-habranch.txt, hdfs-1108.txt
> The current HDFS design says that newly allocated blocks for a file are not persisted
in the NN transaction log when the block is allocated. Instead, a hflush() or a close() on
the file persists the blocks into the transaction log. It would be nice if we can immediately
persist newly allocated blocks (as soon as they are allocated) for specific files.

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