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From "Hairong Kuang (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-1070) Speedup NameNode image loading and saving by storing local file names
Date Thu, 14 Apr 2011 22:26:07 GMT

     [ https://issues.apache.org/jira/browse/HDFS-1070?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Hairong Kuang updated HDFS-1070:
--------------------------------

      Resolution: Fixed
    Release Note: 
This changes the fsimage format to be 
root directory-1 directory-2 ... directoy-n.
Each directory stores all its children in the following format:
Directory_full_path_name num_of_children child-1 ... child-n.
Each inode stores only the last component of its path name into fsimage.
This change requires an upgrade at deployment.
          Status: Resolved  (was: Patch Available)

I just committed this. Thank Matt for his great effort in pushing this jira forward!

> Speedup NameNode image loading and saving by storing local file names
> ---------------------------------------------------------------------
>
>                 Key: HDFS-1070
>                 URL: https://issues.apache.org/jira/browse/HDFS-1070
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.23.0
>
>         Attachments: trunkLocalNameImage.patch, trunkLocalNameImage1.patch, trunkLocalNameImage3.patch,
trunkLocalNameImage4.patch, trunkLocalNameImage5.patch, trunkLocalNameImage6.patch, trunkLocalNameImage7.patch,
trunkLocalNameImage8.patch, trunkLocalNameImage9.patch, trunkLocalNameImage9.patch
>
>
> Currently each inode stores its full path in the fsimage. I'd propose to store the local
name instead. In order for each inode to identify its parent, all inodes in a directory tree
are stored in the image in in-order. This proposal also requires each directory stores the
number of its children in image.
> This proposal would bring a few benefits as pointed below and therefore speedup the image
loading and saving.
> # Remove the overhead of converting java-UTF8 encoded local name to string-represented
full path then to UTF8 encoded full path when saving to an image and vice versa when loading
the image.
> # Remove the overhead of traversing the full path when inserting the inode to its parent
inode.
> # Reduce the number of temporary java objects during the process of image loading or
saving and  therefore reduce the GC overhead.
> # Reduce the size of an image.

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