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From "Todd Lipcon (Resolved) (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (HDFS-3023) Optimize entries in edits log for persistBlocks calls
Date Thu, 01 Mar 2012 00:37:57 GMT

     [ https://issues.apache.org/jira/browse/HDFS-3023?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Todd Lipcon resolved HDFS-3023.
-------------------------------

          Resolution: Fixed
       Fix Version/s: HA branch (HDFS-1623)
    Target Version/s: HA branch (HDFS-1623), 0.24.0  (was: 0.24.0, HA branch (HDFS-1623))
        Hadoop Flags: Reviewed

Committed to HA branch.
                
> Optimize entries in edits log for persistBlocks calls
> -----------------------------------------------------
>
>                 Key: HDFS-3023
>                 URL: https://issues.apache.org/jira/browse/HDFS-3023
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node, performance
>    Affects Versions: HA branch (HDFS-1623), 0.23.2
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>             Fix For: HA branch (HDFS-1623)
>
>         Attachments: hdfs-3023-HDFS-1623.txt, hdfs-3023.txt
>
>
> One of the performance issues noticed in the HA branch is due to the much larger edit
logs, now that we are writing OP_ADD transactions to the edit log on every block allocation.
We can condense these calls down in two ways:
> 1) use variable-length integers for the block list length, size, and genstamp (most of
these end up fitting in far less than 8 bytes)
> 2) use delta-coding for the genstamp and block size for any blocks after the first block
(most blocks will be the same size and only slightly higher genstamps)
> 3) introduce a new OP_UPDATE_BLOCKS transaction that doesn't re-serialize metadata information
like lease owner, permissions, etc
> 4) allow OP_UPDATE_BLOCKS to only re-serialize the blocks that have changed for a given
transaction

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