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HDFS, mail # dev - Issue of FSImage, need help


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Re: Issue of FSImage, need help
Denny Ye 2011-06-28, 09:11
*Root cause*: Wrong FSImage format when user killed hdfs process. It may
read invalid block
number, may be 1 billion or more, OutOfMemoryError happens before
EOFException.

How can we provide the validity of FSImage file?

--regards
Denny Ye

On Tue, Jun 28, 2011 at 4:44 PM, mac fang <[EMAIL PROTECTED]> wrote:

> Hi, Team,
>
> What we found when we use the Hadoop is, the FSImage often currupts when we
> do start/stop the Hadoop cluster. The reason we think might be around the
> write to the outputstream: the NameNode may be killed when it
> saveNamespace,
> then the FsImage file doesn't complete writing. Currently i saw a
> previous.checkpoint folder, the logic of saveNamespace is like:
>
> 1. mv the current folder to the previous.checkpoint folder.
> 2. start to write the FSImage into the current folder.
>
> I think there mightbe a case if the FSImage is currupted, the NameNode can
> NOT be started, but we can NOT get any EOFException, since we might
> encounter the OutofMemory exception if we read the wrong numBlocks and
> instantiate the Blocks [] blocks = new Blocks[numBlocks] (actually, we face
> this issue).
>
> Any suggestion to it?
>
> thanks
> macf
>