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From "Yoram Arnon (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-101) DFSck - fsck-like utility for checking DFS volumes
Date Fri, 24 Mar 2006 00:43:20 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-101?page=comments#action_12371658 ] 

Yoram Arnon commented on HADOOP-101:
------------------------------------

This is a good and awaited feature, filed previously as bug hadoop-95. I vote to check it
in, because as you say, it's much better than anything we have, and of critical importance.

Regarding performance, clearly the nameserver will not be overwhelmed, but the operation may
take a very long time to execute. It's one thing to traverse a million entries in memory (for
a modest 32TB FS), but another matter to execute a hundred thousand RPC calls from a single
client. Also, when we change the open command to not return the entire list of blocks, in
the interest of shortening the time of opening a file, especially when reading just a few
blocks from a very large file, the implementation will need to change.

Lastly, there's extensibility. We'll want to test for things that are available only on the
name server, like blocks that are not used by any file.

Wouldn't it be better to request the server to execute this code internally, and report results
either to the client or to a local file?

> DFSck - fsck-like utility for checking DFS volumes
> --------------------------------------------------
>
>          Key: HADOOP-101
>          URL: http://issues.apache.org/jira/browse/HADOOP-101
>      Project: Hadoop
>         Type: New Feature
>   Components: dfs
>     Versions: 0.2
>     Reporter: Andrzej Bialecki 
>     Assignee: Andrzej Bialecki 
>  Attachments: DFSck.java
>
> This is a utility to check health status of a DFS volume, and collect some additional
statistics.

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